The stamping of the name on Bach trumpet mouthpieces has varied over the years. Below are some general guidelines to help determine the age of Elkhart Bach trumpet mouthpieces. The dates are approximate.
"VINCENT BACH CORP" (no period) 1965-1969
.
"VINCENT BACH CORP." With period that is deep and far from "P". 1970s
.
"VINCENT BACH CORP." With shallow period near "P". 1980s-early 1990s
.
"VINCENT BACH" (no CORP.) 1994-1996
.
"VINCENT BACH" Large letters. 1997-2003
.
"VINCENT BACH" Small letters, no "CORP", but with new "font". 2004-
"VINCENT BACH CORP" (no period) 1965-1969 
"VINCENT BACH CORP." With period that is deep and far from "P". 1970s 
"VINCENT BACH CORP." With shallow period near "P". 1980s-early 1990s
"VINCENT BACH" (no CORP.) 1994-1996
"VINCENT BACH" Large letters. 1997-2003 
"VINCENT BACH" Small letters, no "CORP", but with new "font". 2004-