I understand-- numbers can be scrambled, inverted, etc. Or, in one case of looking for complete SN-- sometimes the front receiver ring area where the SN is stamped, can be partially obscured by a scope base--

The BATFE, IMO, is not usually tolerant of "clerical errors"--IMO, they tend to operate on the "You are guilty"-- because we think you are. In my neck of the woods, two smaller sporting goods shops lost their FFL due to "improper records keeping" on consigned guns-- murky waters, indeed..

"The field is the touchstone of the man"..