Mine is a 2007 date code and serial numbers match.
I've been thinking of cleaning up the frame on a particularly gnarly police trade in. I havent tried it yet but reading on a Glock forum people simply sanding them out with progressively finer sandpaper. I havent tried it yet but looks like it can be done. I suspect it will be shinier or duller than the rest of the frame. Decided it was likely only worth it if I was going to buff/polish the whole frame or cerakote it after I got the gouges out.
as for your second issue, I don't know about working on the polymer with an abrasive, but I suspect there are guys on here who are knowledgeable in such practices...
USP Tactical .45acp
HK 416 10.5" upper
HK45T (OD Green)
I know both my full size and compact were in the first batches of guns to make it to the Northwest. Each came in the first batch of 10 guns the largest HK dealer in the NW got. I was calling them nearly daily getting updates on the delivery, when each gun came in, I took the day off work, and drove 2 hours to get them (I think it was late 2006 for the full size and mid 2007 for the compact).
I hope this is not a derail...
Is there no comparable "proof house" in the USA, like the Ulm proofing with the Crossed Antlers?
Is this proofing required in Germany, but simply not a requirement for "made in USA" pistols in general?
Of all the "missing" markings on the US Hk's, this is the one I'd like to see.
Although, I personally own one used DE HK45 and a sparkling new US HK45.