"Elegant and Practical"
"Mens Push Studs"
Easy Cuff Links in other words..
You just push the 2 halves together to do up your cuffs.
There is a mottled marble like pattern on each side, which is actually celluloid.
Lovely colour variations and each one is different.
They come on their original display cards - I found several boxes of these in an old warehouse I cleared.
They could be earlier than the 1950s as many things in the warehouse were from the 1930s and 40s.
Made by Prym - famous for making press-studs and other haberdashery items.
I have these in the 4 colours shown - please choose which colour you'd like, or have all 4.... to cover every sartorial situation.

Just found another colour- caramel - see last variant.