Here is an original, Kaspar "Cicero Ilinois, 13" from I believe the 1960's. This mouthpiece measures .045" on my gauge.
If you are a classical clarinetist, it's likely that these Kaspar pieces need no introduction. These were produced by Frank Kaspar, not to be confused with his cousin, Frank L Kaspar who produced mouthpieces out of Ann Arbor, MI. These were produced by finishing top quality Chedeville blanks and played on by many legendary clarinetists, included the great Robert Marcellus.
Please note that there is wear on the beak from teeth. This mouthpiece was played professionally and has never been altered.