Here's what i got from jon:
"As for the AFT engravings for an SBR: the requirement is .03 deep. Our laser will not burn that deep so the markings would not meet the depth requirement. That said, Gemtech, Tactical Innovations, Tactical Solutions, YHM and several other manufactures use the exact same method to identify sound suppressors which fall under the same requirement. This does not make it blanketly OK to do but if they are doing it without problem, one would think that it would likely be OK for an individual who is likely never to have his stuff looked at anyway to do the same. Your call. I can do it if you like or not. I just want you to understand that we are NOT representing that this will completely fulfill all the details of the exact legal requirement. "