Originally Posted by Zdunn89

...1926 .38 police positive special...he [seller] said it did not have a serial number [w]hen he purchased it. He took it to the ATF and they stamped it...

Stamped it? With what? Is the "stamp" visible? Or do you mean that BATF ruled that it was a NFA weapon for which the owner had to buy the $200.00 tax stamp? Please clarify.

Originally Posted by Zdunn89

...and looked up the original serial number...

If there was no number on the gun, how, and where, did BATF look it up? Could it be that the engraved number was a newly-assigned, gunsmith-provided serial number?

Originally Posted by Zdunn89

...but it shows no signs of the original serial being scratched off. Any ideas?

It might've been ground-off or polished-off by a gunsmith or refinisher, and the new, engraved serial number added. It may have been a presentation gun, a gift to a retiree, and the engraved number might reflect that.

Originally Posted by Zdunn89

...Second I found numbers on the bottom of the trigger guard hand engraved that do not match original or aft serial. It reads 08501981 RN #1. Any ideas on what this is and how it effects the value?

What do you mean by "aft serial"? Are you referring to the BATF's determination of the gun's original number?
I suggest that "RN #1" might mean that this gun was one of a pair, or one of a larger set, that had been presented to somebody whose initials were "RN."
Maybe he was a cop or a soldier, and his personal serial or badge number was used as the gun's new serial number. This is quite common, in presentations.
If you can trace who "RN" was, and find more of the history involved, the gun would become very valuable, and maybe almost priceless.

A letter accompanied the gun with a letter from the ATF saying that they had physically restamped the gun and it is stamped in the same spot that the serial number would have been. The letter stated that they (the ATF )had traced the gun and found the original serial number but the stamped in ATF serial is different than he original serial and engraving on bottom

Well then, I can only return to my previous advice, as follows:

Originally Posted by Steve M1911A1

...I suggest that "RN #1" might mean that this gun was one of a pair, or one of a larger set, that had been presented to somebody whose initials were "RN."
Maybe he was a cop or a soldier, and his personal serial or badge number was used as the gun's new serial number. This is quite common, in presentations.
If you can trace who "RN" was, and find more of the history involved, the gun would become very valuable, and maybe almost priceless.

I have to assume that, for some so-far-unknown reason, BATF didn't like the engraved serial number.
Maybe it was because the gunsmith or refinisher did not submit the proper paperwork to BATF, regularizing the serial-number change.