[My Marlin 39A has a serial number of 535. Any ideas?]
Every year's production had three-digit serial numbered guns, since Marlin started each year's numbering anew, usually with a consecutive letter prefix, then with a 2-digit date code.
If it has only a three digit SN, with no letter prefix, your rifle is most likely either a very early (ca.1940) M39a, or a waaay earlier Model 39 ( There IS a difference).
Some more details, even a few pics, would help immensely.
The refinishing wiped out the original receiver finish, which changed from color case-hardening to bluing - so the stamped markings on both barrel and receiver tangs would help.
BTW - If the stock is original to the receiver, the same SN will be stamped into the buttstock wood, in the area of the receiver tang inletting.
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