Coin sizes/diameters for common silver coins. Or, “Will your coin mount fit my coin?”

I sell coin mounts/bezels in my shop, and I’m sometimes asked “Will your coin mount fit my [insert name of coin here]?” Occasionally the coin I’m being asked about is almost the right size, but the diameter is just fractionally too small or too large. If this is the case, I have to tell my potential buyer that the answer is “no” – because that fraction of a millimetre multiplies by a factor of more than three when you’re comparing the circumferences. (Think back to school maths lessons: circumference = pi x the diameter.) And it’s the circumference, not the diameter, which is the important thing when sizing up a coin mount.

To help me answer your queries, I’ve compiled a non-exhaustive list of common silver coins, with their dimensions and silver content. Most of them are British but there are a few from other countries in there as well. I’ve gone in ascending order of diameter.

Coin	Dia. (mm)	Thickness where known (mm)	Value	Total weight	Silver content
Three pence (“joey”) (UK)	16.2			1.20 g	Sterling (92.5%) up to 1919; 50% silver up to 1946
Mercury dime (US)	17.9		10 cents	2.5 g	1916 – 1945. 90% silver, 10% copper
Roosevelt dime (US)	17.91	1.35	10 cents	2.268 g	90% silver, 10% copper from 1946 – 1964. Any Roosevelt dimes minted after 1964 were made of base metal.
Sixpence (UK)	19.41			2.83 g	Sterling up to 1919; 50% silver up to 1946
Shilling (UK)	23.59			5.65 g	Sterling up to 1919; 50% silver up to 1946
US silver quarter	24.3			6.25 g (1796 – 1964)	90%. A 40% silver version weighing 5.75 grams was also minted till 1976
Florin (UK)	28.50		Two shillings	11.31 g	Sterling up to 1919; 50% silver up to 1946
Five Deutschmark (W. Germany)	29	2.07		11.2 g	Silver content 62.5% from 1951 – 1974
Kennedy half dollar	30.6	2.15		12.5 g (90% silver version)	90% silver (1964); 40% silver (1965 – 1970)
Half crown (UK)	32.31		2 shillings & sixpence	14.14 g	Sterling up to 1919; 50% silver up to 1946
Ten Deutschmark (W. Germany)	32.5	2.25		15.5 g	1972 (to commemorate the Münich Olympics) – 62.5% silver
Peace dollar (US)	38.1			26.73 g	1921 – 1935. 90% silver and 10% copper
Morgan silver dollar (US)	38.1	2.4		26.73 g	1878 – 1904, 1921. 90% silver, 10% copper
Crown (UK)	38.61		5 shillings	28.28 g	Sterling up to 1919; 50% silver up to 1946
Maria Theresa Thaler	39.5 – 41			28.07 g	83.3%
Silver eagles (bullion version)	40.6	2.98	One dollar face value	31.103 g	1986 – present. 99.9% silver