That’s because the entire country was using l.s.d… or pounds shillings and pence.
From
https://www.retrowow.co.uk/retro_britain/old_money/origins_of_lsd.html
The reason we used ‘d’ for pence is that ‘d’ stood for denarius. Of course ‘s’ can stand for shilling or solidus and ‘l’ stands for ‘libra’, the Roman pound. So 12 denarii (‘d’) made one solidus (‘s’) and twenty solidii made one pound (‘l’).
How many Guinness in a Sovereign? Depends on how long he’s been drinking.
See also horrible histories:
Very true of the time. Also LSD* was in common circulation. 
In decimal: 0.9523809524
In l.s.d. thinking: 20 21st’s is the sovereign portion of the guinea
Following the 1816 - Great Recoinage a Sovereign Coin was fixed to equate to 1 Pound (£1 Sterling) that contained 123.2745 grains of gold (22 carat).
BTW, " The basic unit of currency in medieval England was the silver penny or Sterling, weighing about 1⁄240 of a tower pound."
I am very glad @CodaCoder is showing the Great Brain of the @Mark_S …
Back in the day @Mark_S solved a difficult social-maths issue for me converting between Papua New Guinea OKSAPMIN Countiing (base-27) and decimal and back.
Result …
See: Google Group: Number Base Conversion Macro (2019)
I’m pretty sure I never saw that diagram.
There are memory systems based on body parts. Like a portable memory palace. This seems similar. Was there a taboo against using the lower parts, I wonder? You could triple your counting base, in possibly amusing ways.
That is a shame. It was supposed to be a kinda tx.
Plausibly. But also I’d say it’s plausible you’d avoid them for simple convenience - not as much can be reached easily, and if sitting (making more reachable) then what’s visible and relative positions of body parts change. Would the extra complications be worth it?
@nemo as part of the Sitting Generation I agree the unmentionables have a lacklustre confinement.
Prior to The Chair it was different.
Oh, you’re right. I left the memory on the wrong elbow.
I have strong suspicions that people have been sitting since before the invention of walking upright (which, to be fair I wasn’t there, but I suspect predates the invention of the chair by at least four days)
In The Squat (sitting before chairs) the unmentionables are less constrained.
Back to the old currencies. In retrospect they look absolutely rediculose, and hevens knows I am glad I live in a world of Decimal coinage and meters/kilometers.
Howevwer I did discover something all by myself decades ago. I was studying the primes, and was looking at the numbers near them, and wrote a program to identify the opposites, numbers with a high divisibility. What popped out was all these numbers we see in many places and wonder why they were chosen?.
To put it this way many of these divisions between currencies, or compas directions, hours, and Minutes allow for comon divisions. For example bread roles were often sold in the dozens because it could be divided into lots of 1, 2, 3, 4, or 6. And yes the bakers dozen 13 was to ensure if one role was no good they still had 12 to sell. A bit like a check digit.
This is quite interesting when you look into it, not to mention primes, which is an obsession of mine. Now thats another story.
And for another miscellaneous fact from arithmetic, the number of milliseconds in a day is
11 × 22 × 33 × 44 × 55
which for some strange reason, I find to be delightful.
Had always thought the bakers dozen was a layout to allow bread to raise, and avoid them sticking together as in here
But a Google search didn’t return any results of said layout
It would be really amusing to run across such a thing in my local grocers.
“The other shops only give you twelve!”
“bakers dozen”, Gives it a way. Since most people bought bread roles as a dozen, by adding a 13th there was room to account for one that was over or undercooked and still keep a dozen. Clearly on average 1 in 13 may not be perfect and you could even estimate the number of dozens you bake and expect to sell, on a good day you may have an extra dozen to sell, rather than be a dozen short.
Why do people buy it in the dozen (12)?, because they can be divided among 2, 3, 4, 6 and 12 people without “breaking bread”.
Sorry repeating myself 
