Curious to know if anyone here has sent off a serial number (or multiple numbers) to the CMP to see if they originally sold that gun, and if so, get a letter stating model, grade, and date sold.  Did it pay off when selling the gun?  Just nice documentation to have?  Would you do it again?

I realize the obvious catch is that you pay for the research whether or not they find any records, but I have two 1903s that look like Greek returns with the "B" marked floorplates, and an M1 carbine with Italian arsenal stamps, that I'm reasonably sure came through the CMP, and I'm kicking around the idea of getting them 'lettered.'

I don’t know that CMP provenance adds much value.

Fair.  I imagine that any savvy buyer would put 2 and 2 together and realize they are most likely CMP guns anyway.

Although, and this probably goes more for Garands, the CMP certificate at least means you aren't dealing with a welded receiver.  I guess for 1903s, would also reassure that it wasn't a drill rifle.  Easily confirmed visually if you had it in hand, but if selling online, might put a prospective buyer more at ease.

This.

Other than knowing there will be no import marks

However I will add that it adds value to a Garand if it is an M1C or M1D.  Then you know it's original and not a recent remake.

If you have what you think is a TI or TII National Match and they have a sale record to prove it, IMO it is money well spent.

Most of those are old DCM records managed by the current CMP.