Government of Ontario
Ministry of the
Solicitor General

CFS - TIS - Chemistry - Serial Number Restoration

Centre of Forensic Sciences

Technical Information Sheets


Serial Number Restoration – PDF, 157 kb


A serial number is a unique sequence of numbers and/or letters applied to an item by the manufacturer for the purpose of identification. Firearms are typically marked with a serial number during manufacture however firearms manufactured and/or marketed in the United States prior to 1968 may not possess a serial number as it was not until 1968 that U.S. legislation made it a requirement.

The most common methods of applying a serial number include stamping and laser etching. The success of any serial number restoration attempt will depend on the method in which the serial number was applied and subsequently removed. The restoration attempt is conducted using magnetic and/or chemical techniques that may be destructive, as the procedure most often involves the removal of material. In addition, this examination may require the disassembly of the firearm thereby altering the condition of the firearm from how it was received.  It is for these reasons that all other necessary firearm examinations should be completed prior to attempting a serial number restoration.

The Centre of Forensic Sciences will not attempt to restore a serial number where a previous attempt has been made.


A serial number restoration attempt includes some or all of the following:

  • Inspection of the obliterated area
  • Disassembly of the firearm
  • Search for a hidden, partial or complete serial number
  • Polishing
  • Magnetic and/or chemical techniques of restoration
  • Application of gun oil to the treated area to prevent corrosion


Examples of results that may be reported include:

  • The serial number on the frame of Item 1 could not be restored.
  • The serial number on the frame of Item 1 was restored and reads A95056.
  • The serial number on the frame of Item 1 was partially restored and reads “A95?56 where the “?” is either a 3, 8 or 0.
  • The serial number on the frame of Item 1 was partially restored and reads “A95?56 where the “?” could not be restored.
  • The partial/hidden serial number on the slide of Item 1 reads “056”.