There's always a seller that thinks a military designation is a free pass to a high price. I've seen this more often with trumpets and cornets;- and there are collectors that buy military instruments only, but generally due to specific known history of the instrument, not plausible rumors.
I have a good number of them myself, but I bid on these like I bid on any other instrument of the same make and model. History is only valuable to museums and historians. And that makes it valuable to me, but I don't think of history as something to be owned or sold at a profit. You find the history, then everyone has it regardless of who owns the artifact or becomes the temporary caretaker.
For instance I looked at the history of my USQMC (1922 and later) clarinet and bassoon, both by Bettoney and these plausibly were played at some very significant performances. These included presidential inaugurations, foreign diplomatic ceremonies, the dedication of the tomb of the unknown soldier, etc. These instruments were played when Sousa was conducting the Army band. When it comes to later designations, mostly US and USN, the history of a specific instrument is more difficult to trace and depends mostly on the owner's records or other inscriptions on the instrument.
If it was a USN instrument in use on air craft carriers, expect the springs and rods to be a corroded nightmare. I have one such USN clarinet that belonged to an officer and gentleman apparently named "Andrews" as this is stenciled on the case. I call it the Harry & Harry USN model. It has Bettoney joints with Pedler barrel and bell;- all with military markings. Practically every key rod was sawn through and many had been drilled out. These were replaced with rods that are too narrow to fit well and the keys wobble all over the place. The clarinet plays absolutely perfectly from top to bottom. For something with more hack repairs than I've seen on any dozen other clarinets, it's a beauty.

Well, in the eyes of this beholder, it is.
But the price was right;- $10 plus shipping, which was also quite low. Some of the sellers understand the kind of work it would take to put something right and just hope a good restoration tech will at least use the parts. I can fix this one, but what's the point? It's already a player and has some interesting history just like it is. I oiled the bore. It was dry as desert.
The PM Artist in question is particularly interesting regarding the price. True, it is two different serials, but fairly close together;- I'm not sure what effect the Noblet barrel would have, but it's not going to be as close a match as the Harry & Harry parts are. Those even look the same! A Noblet barrel marked US? That is curious. Perhaps this instrument was still in military use after Penzel Mueller was out of business and the Army bought some barrels from Noblet? That's an odd ball.
That said, the number of Penzel Mueller new listings has recently fallen drastically. There are very few showing up compared to a year ago. There is not an infinite supply of these and sooner or later the supply of PM clarinets will fall below demand. That could be temporary depending on the whims of collectors and players, but these are not like Conn or Pedler or H&A Selmer or even Bettoney as far as production numbers. PM just did not build nearly as many instruments. That seller is wise to start high and run long right now. They might get a $200 - $300 offer eventually or even higher. That is one of the silver plated key models also, but nothing else too special. What is on the keys is mostly the silver sulfide tarnish and that can be reversed pretty easily without removing any silver. It looks like the keys on my favorite 7-ring Pedler, which I did not polish or attempt to return to shiny silver. IMO these PM clarinets are as good as many clarinets with better reputations, and reputations are subject to amendments over time.