They have a shank on the back
so that the 2 open
'button holes' are not filled with thread
and the underneath fabric can peek through.
These are vintage, we do not when they were made or what type of metal this is.
The finish on many of these is not smooth but has some unevenness to it.
*****
Size: 28mm (approximately 1-1/8")
You will receive 12 silver colored buttons.
Thank you!