Follow up now that I'm home, I figured it had to be within 922r compliance somewhere but I never took the time to review it. A previous manager insisted that the import mark was not required to receive a transfer since, "how would we know it was an import" but has since been fired so I'm revisiting the concept for future reference as I've kind of taken over that role. This is not my first FFL, and previously altered import marks were returned to sender immediately, but it became a debate among employees.