Hello everyone,

Does anyone know how Bach serializes it F attachment rotors? I am referring to the number stamped at the base of the rotor casing, between where the tubing enters and exits the valve. As I'm sure that everyone is aware, the number differs from the serial number on the slide. Is this simply a separate serial number for the valve section? I suspect that this is not, since straight bells have no corresponding numbering on the bell section. I'm also curious if the numbers are sequential across the company's entire history. Meaning, if the rotor is No. 75, 000, it is literally the 75,000th one manufactured for an F attachment.

No. I think any numbers on bell sections are assembly numbers, just meant to keep the right parts together through manufacturing.

Only way to date a bell section with no matching slide is to guess by the bell stamp and other features.