FN sxs are not common in this country, but I wouldn't call them all that rare either. I'm sure there are more of them floating around in Europe. One will pop up, every now and then, on some dealer's inventory. It has a good name, but it's not worth a lot due to the fact that it's a very basic gun (plain, unengraved) and shows a fair amount of wear--and is somewhat tampered with.

If it's factory 2 3/4", one of the proofmarks should read 12-70.