On another thread a person posted pictures of a recently made 25-06 and it was stamped 25-06. I questioned that it should be 25-06 REM. On mass produced guns it would be, but I'm guessing custom mades are different. For example mass produced knives made in USA after a certain year are required to have USA stamped on them but this apparently doesn't apply to custom made. What are the guidelines for non mass produced guns?

No official guidelines. All personal preference and CYA. BATFE stipulates that all firearms made originally with serial #s or after a certain date must have serial numbers/characters imprinted to a certain minimum depth.

I don't know what the depth is, but have been told that the common electro-etching is not satisfactory for a serial #. Perhaps they're wanting something that will respond to acid or X-ray when the serial # has been defaced, who knows?

Re your caliber stamping, IMO either is fine since Remington copied the 25-06 cartridge.
Regards, Joe

Joe, must only the serial numbers/characters be left on? What about the original manufacturer's name?

Rob, my source didn't mention that. I guess you'd hafta ask the BATFags, and I'll bet you'll get different answers from different folks.

I don't own an electro-etcher but wish I did. Also wish I could engrave...similar pipe dreams.
Regards, Joe

Is the chamber stamp required by law?

Caliber designation is required by law. And upon a rechamber it must be remarked with new designation.
My .275 Rigby is marked as such when it was rechambered to 7X57, nearly as easy as rechambering a .280 rem to 7mm rem express

I believe is Consumer product safety commission that handles the Caliber markings. They are Federal so it law of the land. And there in-lies the problem. As we try to hunt down laws that pertain to firearms, Not all of the laws that govern firearms are under on roof.