I find looking in my box of old ROMs, a set of 342-0220/21 (no letter), a set of -As and a set of -Bs, so I guess I have both versions plus a possible third version. There's also a set of Beck-Tech 64K upgrade ROMS which support large memory up to 4MB. Question: will a set of -A ROMs work in a Mac that shipped with the -B version? I don't remember what the differences are (if I ever knew to begin with.)

I seem to recall that one set of ROMs revised only one of the two chips, though both got new letters. I believe that was one of the 128K (Mac Plus) ROM sets, though, and the fix had to do with booting SCSI. When I have time, I'll try to dump these ROMs assuming my ROM burner for the Apple II still works. It's been in the closet for at least 20 years. If I can get a good read, I'll post the raw files for the curious. I imagine the ROM files are already on the 'net someplace, since emulators need them. I'm not inclined to disassemble and trace the code myself. Did that long ago and it was a lot of work.