I had a Martin Freres Grand Prix Eb clarinet a few years back, and it was a well-built and beautiful little horn. Great tone and intonation. We couldn't place a date on it easily, but given a wrap-around register key (on a boehm instrument) and some other clues, we estimated 1890 - 1920.
We also determined that Grand Prix would have been the top of the line at the time. Wow, I miss that little horn!