These are a pair of “Martin’s margins”. They are approximately mid-1700’s. They have the cracked lens and the missing end to one temple. They appear to be made of steel and horn.
Benjamin Martin (1704-1782) was an optician in London who invented this style of spectacles.
The design was later much copied. Pairs found today are usually of iron or steel with a C-bridge and margins of cattle horn. Luxury models of silver with tortoiseshell inserts seem to have been made.
The historian, J.W. Rosenthal, has observed that the lenses, whether of pebble or glass, all seem to have been bi-convex and their axes were pointed inwards to meet at the normal reading distance. First two pictures courtesy of Glen Johnston. The third picture is courtesy of Mick Parker.
Museum, Spectacles
