The 'A' in 3003/00A is probably just a series designation, to indicate some minor change in the tach.
Looking at mine, my G15 tach reads 3003/00A and my Ranger tach reads 3003/00B. Both look identical. I don't know if they're original to the bikes, but the G15 goes back to at least 1971 and the Ranger to 1984, the years they were bought by the previous owners.