I just purchased a P220 as a police trade in. The slide is worn and is marked "Made in Germany". There is no serial number on the slide or barrel. The barrel just says 45 Auto. The serial number only appears on the frame: G356 78X. There are no proof marks anywhere. There isn't a date code anywhere either. The frame looks in really good shape, dirty but cleaned up nicely. The slide however looks like it losing its finish and going brown in some areas. The frame has 4 small dots drilled in it near the recoil lug. My questions are: 1), is the slide a replacement by some armorer during the gun's lifetime? 2) what do the 4 dots mean? 3) with the absence of proof marks, does this mean it was assembled in the USA?

The serial number listing on the forum would place this around a 2004 made gun.

You're opinions?
Thanks
Chris

The four “dots” are almost certainly on the locking insert which is a separate part, not the frame. SIG locking inserts have been marked in many different ways, but each specific way was evidently intended to indicate for which model pistol they are designed to be used.

I assume the slide is formed and welded carbon steel, and the blue finish on those slides was not very durable. If you’re seeing brown, that’s because rust is forming and efforts should be made to remove it and protect the steel in the future.

Others may be able to provide more information about the gun’s history, but I believe it was assembled in the US or at least exported from Germany without intending to be sold there and therefore didn’t have the triple serial numbers, date codes, or German proof marks. There may be a proof mark consisting of the letter P in a circle on the locking lug of the barrel. My agency had P220s in that serial number range and with similar characteristics.

Added: Photos would be useful.

It's to ID different locking inserts for different types of P22Xs.

P220s have 4 dots, others have 5, etc.

Wow! Its amazing what you can learn if you just ask the right people. Thank you. The slide is folded/welded steel. I'll try some oil and 0000 steel wool to knock the rust down. Then maybe a cerakote to make it last a little longer.

Thank you for correcting me on the locking block. I don't have a schematic handy and took a swag at the name.

I was going to add pictures, but I forgot how on this forum. Time for more research on my part!

Thank you
Chris

I upload to Imgur to share. There are other ways I'm sure. Love my trade-in 45