a genuine pistol barrel on the left and a fake supposed 15th century barrel on the right, with their x-rays to prove it.

Screw threads as indicators of date

The question

When there is doubt about the authenticity of an object, it may be closely scrutinised to match the technology used in its manufacture with what is known for the period.

Developments in the method of cutting screw threads and the adoption of standardised sizes are often informative. When threads are internal and cannot be unscrewed, X-radiography may be used.

Results of analysis

A genuine late C16th hand cut thread on the breech plug of an English snaphaunce pistol barrel on the left of the image and a supposed C15th hand-gun, fabricated using modern Whitworth thread shown on the right.


The development of screw-thread technology can provide good evidence of the age, life history and authenticity of many historic museum pieces.


Evidence from the X-radiograph of the thread holding this gun together provided key evidence for negotiating with the auction house that supplied it.

Did you know?

4 Eiffel Towers

During the siege of Sebastopol the British fired about 10,000 tonnes of iron shot; the French fired 510,000 round shot, 236,000 howitzer shells and 350,000 mortar shells – a total of around 43,000 tonnes of iron! About the same weight as 4 Eiffel Towers.