Keith Burton's photos with the keyword: Corners

Guess what these were used for. Clues: These were issued to me in 1968 and they were used regularly until 1971 and occasionally thereafter until 1998. Reading my profile may help. For Macro Dreams ✨ challenges: Guess What and End On. EDIT: The answer is now below. Thank you for joining in.

This is for the Macro Dreams ✨ challenges group. This should fit the challenges of: Jewellery, Cubes, Dark on black, Geometric, Multiple, 5 or more.