This is part of my mother's extensive collection of thimbles. She bought them all over 25 years ago from antique stores before anyone bought anything on the internet, so she paid a lot for them.  

This is a heavy duty steel thimble that wants to make it clear it is English.  In the apex, it clearly says Made in England along with a size 12 marking and on the band it also says, "England".  No maker's mark that I can find.  But, it does have a lovely pattern of diamond shapes. Ring of Diamonds weighs a solid 8.4g. Its opening diameter is 19mm.

I found no holes or dents, and it is perfectly in round.  

I'll be glad to combine shipping if you win several thimbles from me (up to three for the same price as one), just let me know and I will wait for the auctions you bid on to end before shipping.  See my feedback from many collectors who are enjoying these little historical prizes as part of their collection now.