Licensees must legibly and conspicuously identify each PMF received or otherwise acquired (including from a personal collection) not later than the seventh day following the date of receipt or other acquisition, or before the date of disposition (including to a personal collection), whichever is sooner. PMFs must be identified by placing or causing to be placed under the licensee’s direct supervision, an individual serial number on the frame or receiver, which must not duplicate any serial number placed by the licensee on any other firearm. The serial number must begin with the licensee’s abbreviated FFL number, which is the first three and last five digits, as a prefix to a unique identification number, followed by a hyphen, e.g., ‘‘12345678-[unique identification number]’’. The serial number must be placed in a manner otherwise in accordance with 478.92, including the requirements that the serial number be at the minimum size and depth, and not susceptible of being readily obliterated, altered, or removed.