Converting from metric is always tough.

In this piece from the Lancashire Evening Post, there seems to be a bit of a problem with conversions:

A Medieval silver broach dating back 600 years which was discovered using a metal detector in a Lancashire field has been declared treasure. An inquest at Preston Coroner’s Court heard that the 35mm silver dress closure was discovered by a pair of a metal detecting enthusiasts in a farmer’s field in Croston, near Chorley, in October.  The piece is half-an-inch in diameter, with groove decorations around it and a hook believed to have been used to fasten clothes.

35mm or half-an-inch?