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Note the symphonic 4s-1-28 in blue. The 4s ("for symphony") series are the deepest/largest Al Cass standard trumpet mouthpieces made by Al Cass.
The 3 series. 3x1 is deepest (red), The 3x7 shallowest (amythest). Note there is no 3x6 shown, Note the gap between 3x5 and 3x7.
Scan of 2 series rim & cup shape, only variations would be throat size 24-28 and backbore. (A was the only backbore option).