So, the thing is, not only does that serial number not belong on that pistol, that serial number does not belong on that pistol.
Allow me to explain.
Browning's serial numbering scheme in those days told you a lot about their guns. BDAs were offered in three calibers 45 ACP, 9x19mm and 38 Super. Each of these three calibers had their own serial number prefix; 345 for 9mm, 375 for 38 Super, and 395 for 45 ACP.
Your slide shows a serial number beginning with 395RP, which should be a 45 ACP BDA made in 1978.
So, not only does that serial number not belong on that pistol because it's not a SIG serial number, it really doesn't belong because it's a serial number for a different caliber.
And no, it's not a 45 ACP slide at all.
Do you happen to know the proof date on this pistol? The serial number suggests 1978, but as I've stated, the serial number is extra super wrong.
Posted a question on the Sig Forum to find out just what I have. It's an 'old school' Sig, but I think it's new production. No German date code or proof on the underside of the slide and serial number is G 3083XX on the left side of the frame only. Funny, but it's got 'old school' stepped magazines, serrated trigger, and Trijicon night sights. The serial number is S4-504xx (I checked the S4 under high magnification, and it is definitely a '4' and not an 'A'). I sadly noted that the Sig case did not accompany the P239 and the dealer said he will attempt find it. It is ALL stainless, and shows very little 'smiley' wear on the.40S&W barrel.
Sig P220 Serial Number Dating Scams
There seems to be a small run of these P220 in 7.65 with Browning serial numbers. Here are 2 othes I've found...Sig Sauer P220 Serial Numbers
396RP7396 JA 7.65 = Thanks to Dusty Dave (in Serial Number List)
395RP7377 JA 7.65mm Para (posted by Ken* on 8/28/14 in Serial Number List thread)
Sig Sauer P320 Serial Number Lookup
Posted a question on the Sig Forum to find out just what I have. It's an 'old school' Sig, but I think it's new production. No German date code or proof on the underside of the slide and serial number is G 3083XX on the left side of the frame only. Funny, but it's got 'old school' stepped magazines, serrated trigger, and Trijicon night sights. The serial number is S4-504xx (I checked the S4 under high magnification, and it is definitely a '4' and not an 'A'). I sadly noted that the Sig case did not accompany the P239 and the dealer said he will attempt find it. It is ALL stainless, and shows very little 'smiley' wear on the.40S&W barrel.
Sig P220 Serial Number Dating Scams
There seems to be a small run of these P220 in 7.65 with Browning serial numbers. Here are 2 othes I've found...Sig Sauer P220 Serial Numbers
396RP7396 JA 7.65 = Thanks to Dusty Dave (in Serial Number List)395RP7377 JA 7.65mm Para (posted by Ken* on 8/28/14 in Serial Number List thread)
Sig Sauer P320 Serial Number Lookup
395RP7381 falls in between them. I wonder if the 396 prefix on the first is a typo. My theory is that after the importation by Browning ended there were some frames with BDA .45 serials left over and they were completed by Sig Sauer as P220 with new slides and barrels matched to those frames.
Sig P220 Serial Number Date Of Manufacture
Further theorizing (and I'm really going out on a limb here) is that Sig Sauer did not have reason to adhere to Brownings serial number coding and made them up in whatever caliber needed at the time, 7.65 Para to satisfy demand from Italy.Sig P220 Date Of Manufacture
Sig P220 Serial Number Dating
I do not know the date code yet. I hope to have the pistol in hand next week.