early indian i.d. #'s

[RichO]

I just found Indian single #G1569 (4 stud), Indian single #G1600 (4 stud), and Indian single that looks like it was a single with the same cam cover, oil pump, etc as the other two but it's a factory twin case with no provision for rear cylinder lifter parts, etc. No numbers in the number boss. Factory race motor? Any help on year of manufacture for these would be appreciated. Thank you.