a couple I have found is the inside of the ECu, I have heard this is not common, but a few are around. I found this after fitting a HRC ecu(part number 38770-NL5-003) to my bike,
this is inside the standard ecu(part number 38770-MW4C-631)
the sticker on the removable eprom says;
DATA & MAP SET 0
MW4 ED
OCT 93
also when the engine was removed to fit the HRC pistons/cams etc, just above the engine number J105 is hand engraved, also on all the cam caps and other engine components there are lots of hand engraved japanese symbols and numbers.