Trombones carry their serial on the slide receiver or the bell — and at some makers, notably Bach, the bell and slide were numbered separately, so the bell is the section to date from.
On the slide receiver or the bell — date the instrument from the bell. Markings and exact positions vary by maker and era — the serial number guide covers the common locations for every instrument.
15 makers with 1022 dating ranges are listed on this page. Coverage grows as more maker records and historical tables are verified.
Recheck the characters exactly as marked — letters and leading zeros are part of the number. Letter prefixes often belong to student or non-domestic lines, and some production periods are simply not covered yet.