Serial number?
Yep

Not a big deal though, I don't think anybody will care. (No, I don't know where exactly it is located in the dump)
Thanks for the dumps for both of you. FWIW, 100a and 100b won't need separate ports, they are almost completely identical.
@alvm
If possible, please use the official dumper script - the CHDK tools expect dumps starting at 0xff810000 for cams with 8MB ROM.