Dating my 112-65

I was curious if I could find a way to date my music man amp. The chassis number is 2275-65. Its got a huge cabinet with a single 12" speaker. Work was done on it, so it's hard to tell what was original and what wasn't. The serial number is BN00598. Thanks a bunch!

The only true way to date a Music Man amp is to remove the chassis from the cabinet and look for date codes written on the chassis or on labels either on the inside or outside.
The 75 series were only made between 1980 and 1984 so they all fall within that 4 year period.
Steve