Re-arranging the data collected so far with the sequence of each model separated. I think this gives a better idea of how the system worked and is easier to get an idea of when a given serialized model was made, even though in most cases we are guessing.
1892 Founded by G Penzel
G.L. Penzel & Bro. No serial "C" clarinet
1899 P&M partnership
The earliest serialization system certainly appears to be a simple numerical sequence after a few years of no serialization.
Penzel Mueller No serial B (HP) German sys 6-ring
Penzel Mueller # 339 7-ring Boehm (rollers on spatulas, Eb lever for L5) (collection of G. Kern)
1914 P&M, G. Pruefer partnership ? 1914 - 1920 (Source Sax on the web, poster cyclopathic: History:
Pruefer started clarinet company in 1906.
In 1914 he merged with Penzel and Mueller to form Penzel Mueller and Pruefer
In 1920 Pezel had died, Mueller gained control of the company and Pruefer retired
In 1920 Gus Pruefer had traveled to Markneukirchen, Germany and helped Moennig to modernize factory
1921 Restarted Pruefer clarinet company in US (young Hans Moennig joins Pruefer in RI)
1976 Pruefer factory in RI burned
Penzel Mueller Pruefer no-serial LP B 7-ring Boehm, wrap around register key.
Penzel Mueller Pruefer # 3795 LP B (straight lever register key, French ligature & cap)
1920? P&M - Prufer separation. The little information so far leaves some confusing issues. How many clarinets from the partnership had no serials? When the clarinets from the partnership are serialized, does this have any relation to previous or later Penzel Mueller serials or Pruefer serials? Pre WW1 > Post WW1 is therefore one of the more confusing serial periods. There are 3 clarinets with military markings in Penzel Mueller serial area 4700-5400. Are these pre-war or post war serials? Before or after the Pruefer partnership? The serials before the war, during the war and immediately after are still hard to nail down. There is also the duplicated number;- #3795 appearing on a Pruefer partnership clarinet and also on one simply marked Penzel Mueller LP B.
Penzel Müller (reported spelling, unreadable in photo) # 775 Albert / simple 2-ring Eb LP USQMC (instruments made for the USQMC date from just after the end of WW1, apparently early 1920s?)
Penzel Mueller # 3338 LP A (front spiral key, not typical PM wrap around)
Penzel Mueller # 3795 LP B (7-ring, rear register key)
Penzel Mueller # 4036 LP A (front register key)
Penzel Mueller # 4685 B German sys 5 ring USQMC (WW1 era?)
Penzel Mueller # 4743 LP B USN (WW1 era?) (reviewed on Clarinet Pages Therese K)
Penzel Mueller # 5175 LP B Albert
Penzel Mueller # 5267 Eb LP Albert 5-ring
Penzel Mueller # 5393 5-ring Albert "USN" (WW1 era?)
Penzel Mueller # 5746 LP E Albert
Penzel Mueller # 5845 Bel Canto Eb
Penzel Mueller # 6411 LP Eb
Penzel Mueller # 6631 LP B 6631 spiral register
Penzel Mueller # 6839 LP A full Boehm articulated C# (Dave LeBlanc restoring)
Penzel Mueller # 6998 LP B Full Boehm/artic with LH5 Ab
Penzel Mueller # 7214 LP A full Boehm articulated C# (mechanic)
Penzel Mueller # 77xx LP C Boehm system
Penzel Mueller # 7727 LP B 6-ring (bakelite bell, front register key, key part substitution LJ ?)
Penzel Mueller # 7769 LP B 7769 has spiral register, (collection Silversorcerer)
Penzel Mueller # 7902 LP C Albert/German system
Penzel Mueller # 8270 LP A (Phil Pedler)
Penzel Mueller # 8458 LP B (straight lever register key, bakelite bell broken) traveling with Pan American bell now
Penzel Mueller # 8739 LP B 5-ring Albert
Penzel Mueller # 8855 LP B (My father had this before taking up the oboe when in H. S band. He was born 1911 so this should date before 1928.)
Penzel Mueller # 8937 LP A (bbranha)

?? Penzel Mueller # 9031-C (this one is hand serialized and is a Boehm clainet in the key of C, quite unique)
Penzel Mueller # 9250 LP B 9250 has straight lever register key (still mark LP Bb) (collection Silversorcerer)
Penzel Mueller # 9544 LP A (traveling with Buffet barrel and Barbier bell)
Penzel Mueller # 9934 June 1927 Sale's receipt for #9934 Penzel Mueller LP B Albert #5
Penzel Mueller # 10790 LP B 7-ring, Bakelite bell, flush band UJ (well done) traveling with Jacques Albert Fils & unmarked barrels
Penzel Mueller # 10893 LP B
Penzel Mueller # 10973 LP B
Penzel Mueller # 11111 Full Boehm
(Beginning of named models, Artist and Empire State, later "M" and "H" models (date = 192? - 193?) and plausibly roughly coincides with discontinuance of "LP" designated instruments with adoption of USA A=440Hz standard.)
Penzel Mueller # 1xxx1 Artist "A" articulated C#/G#
Penzel Mueller # 11601 ?
Penzel Mueller # 12543 LPB Albert #5 USQMC
Penzel Mueller # 12835 Empire State ("B" above model name, original serial locations, no B suffix, early key type, early thumb rest, block letter style embossing, Bakelite bell)
Penzel Mueller # 13092B Empire State (scratch or H or F prefix?, "B" above model name, original serial locations, B suffix, early key style, block letter style embossing, wood bell with no markings shown, possibly substituted for an original Bakelite bell)
Penzel Mueller # 13103B Empire State (no "B" above model name, original serial locations, apparently no letter prefix, early key style, block letter style embossing, Bakelite bell)
Penzel Mueller # H13163B Empire State ("B" above model name, original serial locations, B serial suffix, early key type, early thumb rest, block letter style embossing, bell and barrel missing)
Penzel Mueller # 13460 ("B" over trademark, no model name, no prefix or suffix, no LP designation.)
Penzel Mueller # 13695 Artist (Alfearless, UK)
Penzel Mueller # 13888 Artist (7-ring articulate C#, pinned upper joint)
Penzel Mueller # 13919 Artist
Penzel Mueller # 14280 Artist (collection Silversorcerer)
Penzel Mueller # 14386 Artist (articulated C#/G#)
Penzel Mueller # 15082 Artist (7-ring articulated C#/G#) (There is evidence that this clarinet had an auxiliary Ab key between the left hand Low E and F# keys but it has since been removed and discarded by a previous owner)
Penzel Mueller # 15448 Artist
Penzel Mueller # 15547 Artist
Penzel Mueller # 15586 Artist
Penzel Mueller # 15601 ?
Penzel Mueller # 15607 Artist A
Penzel Mueller # 15836 Artist
Penzel Mueller # 16216 Artist (articulated C#/G#)
Penzel Mueller # 16613 Artist (serials to new locations no pre-fix, no suffix, Genuine Grenadilla, Patent applied for on bell, pinned upper joint)
Penzel Mueller # 17205 Artist (serial number locations moved to trills and RH5 cluster)
Penzel Mueller # 17444 Artist (collection A Bellows)
Penzel Mueller # 18542 Artist (7-rings, articulated C#, two side key touches between LJ rings)
Serial Format changes (Date = 193?)
The letter designated models each had their own serial sequence so what we have so far with a small data sample allows only a very loose date estimate for most models. The application of letters seems to closely follow the relocation of the serial number embossings. "M" series begins as Artist model, "H" series as Empire. The "R" Bel Canto model was added, much later Brilliante replaced Artist as "M", "L" was added and became the new Artist. During the post WW2 era, the "U" student models appear sometimes with additional pre-import serials. The U models are both domestically produced and imported. It appears that the very last clarinets Penzel Mueller produced were the "SM" or "SL" Super Brilliante models. Others with "B" serials with no letter prefix bearing names such as Studio Recording and Soloist might also be among the very latest produced.
"H" model Serials:
(Plausibly the "H" designation begins around 1930, perhaps replacing the "LP" models. Production of "H" Empires continues until all production ceases.)
Penzel Mueller Empire # H127B (collection Silversorcerer) (silver plated tear-drop keys, wood bell, original fitted case)
Penzel Mueller Empire # H924B
Penzel Mueller Empire # H977B
Penzel Mueller Empire # H1052B (teardrop keys, traveling with Artist Bell)
Penzel Mueller Empire # H1318B (German silver keys, wood bell)
Penzel Mueller Empire # H1360B (German silver keys, wood bell)
Penzel Mueller Empire # H-1542 B Empire
Penzel Mueller Empire # H2198B (not tear shaped keys)
Penzel Mueller Empire # H2240B (wood bell, Noneyet, not tear shaped keys, no lower bell ring)
Penzel Mueller Empire warranty for # H-12372 Model # 225W 11/10/1937 (No clarinet photos available, warranty only, and curiously no "B" suffix. Therefore it is unclear whether this warranty references an Empire with the "B" suffix or an earlier Empire which only had a number, the "H" designation appearing on the paper work only?)
Penzel Mueller Empire # H13702B
Penzel Mueller Empire # H14630B
Penzel Mueller Empire # H14898B (collection Silversorcerer) (Bakelite bell)
Penzel Mueller Empire # H15208B (collection Silversorcerer) (Bakelite bell, nickel silver keys)
"M" model Serials:
(Plausibly the "M" designation begins around 1930, first as the Artist, then as the Brilliante. "M" model production continues until all production ceases. 2 SM prefixes appear late, one of which carries the Super Brilliante markings.)
Penzel Mueller Artist # M1068B (The number 1068 is stamped into the back of the E/B lever for the LH5)
Penzel Mueller Artist # M1519B (flat sterling silver rings)
Penzel Mueller Artist # M1719B "USN" (WW2 era?) (pre-Brilliante Artist gets M designation then L?)
Penzel Mueller Artist # M1920B / M1977B "USN" (upper is M1920B, lower is M1977B, barrel is D. Noblet)
Penzel Mueller Artist # M2312B
(introduction of the Brilliante is generally rumored to be post WW2)
Penzel Mueller Brilliante # M3361B (collection Silversorcerer)
Penzel Mueller Brilliante # M3417B
Penzel Mueller Brilliante # M3479B
Penzel Mueller Brilliante # M3736B
Penzel Mueller Brilliante # M3751B
Penzel Mueller Brilliante # M3935B
Penzel Mueller Brilliante # M3966B (collection Silversorcerer)
Penzel Mueller Brilliante # M4032B
Penzel Mueller Brilliante # M4163B Original registration letter January 13th,1947 Walter W. Mueller
Penzel Mueller Brilliante # M4197B (silver plated keys, 17/6)
Penzel Mueller Brilliante # M4236B
Penzel Mueller Brilliante # M4261B
Penzel Mueller Brilliante # M4498B
Penzel Mueller Brilliante # M4535B
Penzel Mueller Brilliante # M4668B (collection Silversorcerer)(Owner died Honolulu 1957 - Ted Wells of Ted Wells and the Band - other web documents indicate activity of owner/player as late as 1954)
Penzel Mueller Brilliante # M4748B (collection G. Kern, tear shaped keys LJ)
Penzel Mueller Brilliante # M5151B
Penzel Mueller Brilliante # M5487B
(possibly entering Korean conflict era, circa 1950)
Penzel Mueller Brilliante # M5898B US, traveling in a vintage Buffet case
Penzel Mueller Brilliante # M6165B appears that something embossed was removed by sanding from bell above Brilliante mark, also on the barrel. Case marked "U.S." looks original. Plausibly this was military issue and the "U.S." marks on the clarinet removed.
Penzel Mueller Brilliante # M6453B "US" (collection Silversorcerer, with reed envelope from Anderson Music Co., Dearborn, MI, est. 1952)
Penzel Mueller Brilliante # M6532B "US"
Penzel Mueller Brilliante # M6537B / M6532B "US" ("This vintage clarinet was used by my Father who was a professional musician in the Glenn Miller era." source = son of owner, seller)
Penzel Mueller Brilliante # M6552B (traveling with a Couesnon mouthpiece, Selmer barrel, and Bettoney case)
Penzel Mueller Brilliante # M6844B "US" (built 1949?, source = seller/unknown/unconfirmed)
Penzel Mueller Brilliante # SM7672B "US" (no Super Brilliante marks)
Penzel Mueller Brilliante # SM7690B "US" (no Super Brilliante marks) 17/6
Penzel Mueller Brilliante # M8012B "US"
Penzel Mueller Brilliante # M8276B "US" (collection Silversorcerer)
Penzel Mueller Super Brilliante # SM8846B
Penzel Mueller Super Brilliante # SM8941B (collection A. Bellows)
Penzel Mueller Super Brilliante # SM9001B (KimM613' father, ".... He was born in 1941 and I remember him saying that he took lessons when he was younger. I believe that this was the only clarinet he ever owned.")
Penzel Mueller Super Brilliante # SM9187B (silver plated or silver keys)
"L" model Serials:
(Plausibly the "L" Artist series begins with the post WW2 introduction of the Brilliante model, which assumed the "M" designation. "L" production likely continues until all production ceases. SL serials appear marked as Super Brilliante late in the serial series)
Penzel Mueller Artist # L103B
Penzel Mueller Artist # L987B
Penzel Mueller Artist # L1085B - "US"
Penzel Mueller Artist # L1104B
Penzel Mueller Artist # L1706B
Penzel Mueller Super Brilliante # SL8984B
Penzel Mueller Super Brilliante # SL8989B
"R" model Serials:
(The R Bel Canto is perhaps the 3rd oldest lettered model, plausibly introduced in the 1930s. It is also apparently rare appearing only sporadically compared to other models from the same period)
Penzel Mueller Bel Canto # R380B
Penzel Mueller Bel Canto # R446B
Penzel Mueller Bel Canto # R777B
Penzel Mueller Bel Canto # R902B (Phil's Gallery)
Penzel Mueller Bel Canto # R964B
Penzel Mueller Bel Canto # R1230B (collection Silversorcerer) (with a curious mark;- a circle around a large "P" super-imposed over a smaller "M" above "MADE IN U.S.A." The embossing is at the bottom back of the UJ.)
Penzel Mueller Bel Canto # R1537B
"U" and other student model Serials:
(Plausibly post WW2, G. Penzel student line begins, some models imported from Europe sporadically until all production ceases.)
Penzel Mueller (G. Penzel) Professional # U237B
Penzel Mueller (G. Penzel) Pacemaker # U875B (Germany, plausibly by Schreiber & Sohne?) # 8477 (collection Silversorcerer)
Penzel Mueller (G. Penzel) Trailblazer # U2265B with 7/573 (Italy? looks like Pastore (stenciled Rampone or Otello Milano?) (collection Silversorcerer)
Penzel Mueller (G. Penzel) Pacemaker # U3744B (France, Tinker73)
Penzel Mueller (G. Penzel) Professional # U7166
Penzel Mueller American Gloritone wood model # gr3134B
Penzel Mueller (G. Penzel) Pacemaker # Vr3247B
Penzel Mueller Jean Aubert # J3380B (only one so far, odd offset A/G#, heavy trill guild, circle P over M marks)
Penzel Mueller (G. Penzel) Pacemaker # O3726B
Penzel Mueller (G. Penzel) Pacemaker # GU4049B (case is rectangular suitcase type typical of late 40s - early 60s)(The number on both keyed parts is GU4049B. Another stamp is 16284 made in Germany.... From my Dad's clarinet shop... His inventory includes many vintage, or otherwise highly valuable instruments....) Source=seller
Later models with no letter prefix but with the "B" suffix (at some point it appears prefixes were dropped possibly because they were redundant). It is plausible that these are among the last Penzel Mueller clarinets produced.
Penzel Mueller Studio Recording # SR 3535B (France)
Penzel Mueller Soloist # 4004B (T-bridge clutch & New York, Toronto, Paris mark) (collection G. Kern)
Penzel Mueller New York # 4701B (T-bridge clutch, key work similar to Thibouville Freres M. Masson)
Penzel Mueller (G.Penzel) Pacemaker # 5221B
Penzel Mueller (G.Penzel) Pacemaker # 5229B (collection G. Kern)
Penzel Mueller Studio Recording # 5366 model (New York, Toronto, Paris, appears to be later model, serial location bottom UJ, top LJ, separate G#/A posts) (collection reedalanb)
Penzel Mueller Bel Canto # 5486B (no R pre-fix)
Penzel Mueller Soloist # 5775B "France" (Original owner selling this Penzel Mueller Soloist wood clarinet. In excellent condition. All parts work and cork in great condition. Used three years in Jr. High school mid 1950's. Has "France" stamped in wood.)
Penzel Mueller (G.Penzel) Pacemaker # 6228B (collection Silversorcerer)
Penzel Mueller Soloist # 6465B (T-bridge clutch & New York, Toronto, Paris)
Penzel Mueller "France" # 7866? Penzel Mueller (looks like Thibouville Freres M. Masson keys)
Penzel Mueller #7967B "France"
Penzel Mueller Super Brilliante # 9212B
1956 - 1960 Somewhere between these years, Penzel Mueller ceases operations entirely. Based on the data compiled so far, total instrument production appears to be 40,000 to 50,000 clarinets. This total is a fairly low production number compared to a maker such as C.G. Conn, Ltd., whose brass instrument production was almost a million instruments in the same time frame.
Metal Clarinets appear to have a separate serial sequence:
American Gloritone
#3855 (Daniel_Bingamon)
#480(?)1 (Gloritone hand incised, surround stamped)
#5357 (stamped bell engraving)
Clari-met
#400 (double wall with separate bell, lower joint, upper joint with integrated barrel, 7-ring full Boehm with articulated C#)
#S1571 (single wall, separate joints, barrel, bell integrated with lower, 17/6)
Artist (keep looking)