Original Specification for Diameter of the Sovereign

[GreyBeardUK]

I have tried to find the answer to this question on the internet to no avail, so I wondered if any of you experts know.

The diameter of the Sovereign is universally defined today as 22.05mm. But when the present Sovereign was first produced in 1816, the Mint would not have used the metric system. We had only just defeated Napoleon, and then, and for decades afterwards, the Metric system was seen as "French". So the diameter must have been defined in Imperial units. But 22.05mm does not appear to convert to any sensible fraction of an inch (either thousandths or e.g. n/32). I did wonder if the size of the blank might have been what was defined, with the finished size being a "bit" larger to allow for the milling. But I can't find a solution there either.

All the sources I can find only talk about weight and fineness. Do any of you know where the diameter came from?

[ZRPMs]

I think the full sovereign is 7/8 of an inch with the half at 3/4. 

[Spyder]

This is a very good question. I know it was to to be half the size of the original sovereign. All to do with grains again that could have been any width with the thickness being different. Without looking to carefully, maybe thickness has stayed the same and only the width has been halved.  You are correct, very little details is available online. 

[GreyBeardUK]

Thanks for the reply, but 7/8 of an inch is 22.225 mm. I'm pretty sure the spec isn't that far off.

But that's what I mean - I would have expected 7/8", or something equally simple...

[Booky586]

I'm not aware of any source document or standard from the 1816 period that specifies the diameter of the sovereign. "The Royal Mint" by Ansell is a good starting point and it's worth a read.

In it he states "The diameter and consequent thickness of a coin are not determined by law, but by it's suitableness for the public to whom it is to be issued; consequentially the usual mode of arriving at the diameter of a coin is too make it of such a size that it will emit the most musical sound it is capable of."

Not bad eh, doesn't matter what diameter it is, so long as it sounds nice! 🤣

Here's a screenshot with some data on coin diameters:

https://archive.org/details/royalmint01anse

[SidS]

5 hours ago, Booky586 said:

Not bad eh, doesn't matter what diameter it is, so long as it sounds nice.🤣

Can't argue with that.

[GreyBeardUK]

Thanks very much for that reference!

So they didn't attempt to use fractions, but whole thousandths of an inch.