Screw threads as indicators of date

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

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.

Significance

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

Output

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

Scary Horned Helmet

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Thunder birds are go!

Artillery pieces before about 1700 were often classified by names. A rare type of very big gun was known as a basilisk, a more common long powerful gun was known as a culverin while smaller versions were named after birds of prey such as saker and falcon.