To be fair I have no idea how large an American penny is - it's not a very precise indication of size for anyone who's not American.
It is reasonably precise, at least "good enough for government work"—the size is federally specified https://www.usmint.gov/learn/coin-and-medal-programs/coin-sp... —just not familiar.
Thankfully we have tamed our penny somewhat, from the wild beast it used to be. It used to be abbreviated to "d" and there were 12 of them to the shilling (s) and 20 shillings to the pound (l ie: £, which is what happens when you get the ink pen out).
In 1971 we decided to stop taking the piss and fall in line with the rest of the civilized world and decimalise: One squid = 100 pennies!
So the US call their cents "pennies". How cute 8) Those odd abbreviations I mentioned earlier - LSD for pounds/shillings and pence. They are sort of derived from libra/sestertii/denarius ie Roman currency units. I've glossed over florins, sovereigns, groats and all the other weird and wonderful coinage of the realm. We were not alone, most countries have some pretty odd past coinage and currency ... or didn't bother and stuck with barter for simplicity.
"Precise" has a precise meaning, and it was a pedantic (though in a way I appreciate) comment on that. Your lack of familiarity with "American" pennies does not change that they are a very well defined size.
This often comes up in science discussions because to many lay people "Precise", "Accurate" and other terms are used interchangeably, when they have distinct meanings
If it's being used for scale in an image, why does it matter if they know the name of it rather than knowing how big it is? Do people need to know who the bearded man is on the front of it as well?
Robert V. Barron, right? ;P
You omit the guinea. I read once that high-end auctions are conducted in guineas so that bidders from all currency areas are equally handicapped.
A guinea is a pound and a shilling - a sort of fat or posh pound I suppose. Horse race prizes here are still priced in guineas eg here's a random link, noting guineas:
https://www.racingpost.com/news/festivals/guineas-festival/c...
I can imagine that in the past, a popinjay or boastfool (made that one up) caused the guinea to be created because they wanted to outflance someone else. I don't think £1 1s is a useful lump of money, ever. I think it is simply there for bragging rights and further nonsense.
There is also the sovereign - "sov" - also a nickname for a pound but it isn't one. Gold sovs are worth a shit load these days.
I also missed out tanners and a lot more 8)
That's cool.