Marking of firearms can be split into two categories:  those FFLs that manufacture a firearm from start to finish and those FFLs that manufacture firearms with parts from third party vendors. Let’s use ATF Ruling 2012-1 to review the marking requirements for each of these two, different manufacturing scenarios. The easier of the two is the FFL that manufactures firearms from start to finish in one continuous flow.  By the time the manufacturing process is complete, the firearm should have been marked with the following: (A) a serial number, engraved or cast, on the receiver or frame of the weapon; and, (B) the model, caliber/gauge, manufacturer’s name, and place or origin on the frame, receiver, or barrel, by engraving, casting, or stamping (impressing) the required information at a minimum depth. Now, what if you are a manufacturer that contracts out to a third party vendor for the frame/receiver?  Then you are going to have two steps involved, and one of those steps will be slightly different than if you were to manufacture a complete firearm at your plant. When a third party vendor is involved in the manufacture of the complete frame or receiver, the vendor is responsible to mark it during the part manufacturing process with the same information as if making a complete firearm.  However, if the model and caliber/gauge is not known to the vendor at the time of manufacturing, these may be omitted.  The ATF also allows vendors and manufacturers to submit requests for a “non-marking variance.”  The frame/receiver is an integral part of the firearm and, by definition, does not include the barrel. If you are the manufacturer contracting to a third party vendor for frames/receivers, the ATF recommends, but does not require, the following records to be maintained to assist with an audit inquiry surrounding the 7-day marking rule: (1) a copy of the current, active license of all contracted licensees; (2) records of firearms production; (3) work orders, contracts, and related instructions for services rendered that describe the various firearm manufacturing processes; (4) orders for firearm parts that have yet to be received; and, (5) invoices to repair non-functioning machines. You can read ATF Ruling 2012-1, along with all the referenced laws and regulations, in the on-line Orchid Advisors research library.