The serial number, 1373 puts this Brilhart at the very beginning of their production in 1939...
This is a very rare Hard Rubber alto mouthpiece designed by Arnold Brilhart, which unlike the popular plastic ones ( ebolin and tonalin) has a pretty big rounded chamber, like the very old Otto Links.
Being paired with its long facing curve it provides a very warm, mellow, free blowing sound. Particularly in the lower register.
This mouthpiece measures 0.074'', which is close to a vintage Meyer 5 tip opening-wise or between a 5 and a 6 more in general.
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