I too have a 128K which has a 342-0220-A/0221 with no letter - however, it does say "REV A" next to the copyright date. It happens to be on my early 13th week, completely original, unaltered 128K. So this is either a mixed ROM set, reflecting an early revision in the product cycle, or an early method to represent the "-A". Do yours have the words "REV A" next to the copyright date?

As for the ROM dump, I sent a -B disassembly file to Paul Pratt to compare to his -A ROM set, and he indicated minor changes. I did not think to send him the 0221 REV A ROM, however. Nevertheless, the 1984 copyright date relates to the Sony drive stepper motor update. Both ROMs will work in either MAC. However, since the fix pertains to the newer 400K drive revision, newer drives are incompatible with the -A chips. The -B chips are backward compatible.