Went out to the field site this evening. Found 2 very old looking bells. One one them was hit by the plough, the other is near mint. I cleaned the dirt out from inside the one and it still jingles!!
If the bells have the maker's initials on the bottom you can usually find out the manufacturer's name and when and where it was made.
A lot of these bells were made in England during the 1700's & 1800's.
Just keyword "Dating Crotal Bells" in Google and it will lead you to the website.