This is an Archimedes calculator, a
Model D.
It was made in Glashütte.
This is a small town in Germany,
very close to the Czech border.
Glashütte is renowned for its precision mechanics, and
this all started in 1845
when Ferdinand Lange set up a watch company there.
The first calculator company to start in Glashütte
was Arthur Burkhardt.
They made Arithmometer types of calculators,
not dissimilar to this one.
A young man who worked there as an apprentice,
he was called Reinhold Pöthig,
he left to join another small workshop
owned by Constantin Fischer,
and a year later, in 1900
there was some kind of bankruptcy proceedings,
Constantin Fisher left, and
Reinhold Pöthig was now the
owner of this small workshop.
At the age of 23 he owned his own company.
He decided to also start making these calculators.
He had seen these calculators at Arthur Burkhardt,
and had his own ideas on how to improve them.
In 1906 he made his first one, the Model A.
By 1915 he was making these the Model D.
These were very successful and lots of
different variants were made.
I think this particular one is a fairly early one,
say around 1917 or 18.
It has a serial number on the edge of this carriage at the top.
You can just about see it here.
It says 3819.
It's a fairly standard Arithmometer type of machine,
but it has a keyboard.
The model D was the first to have a keyboard.
Let me show you how it works.
So you can simply type in a number.
The entered keys stay pressed down.
Here you can read off the number that you've entered.
I've entered 1234.
On the right is a small crank, and
when you turn that the entered number
gets added to the main register here
and the counter gets incremented.
It moves very easily, very smoothly.
So it now says 1234 and here it says 1.
The keyboard was automatically cleared,
so I can now enter another number,
and add that to the total.
So addition is very easy.
To subtract you can flip both of these switches here,
and what that does is, now when you turn the crank
the number that you've put in gets
subtracted from the main register
and the counter gets decremented.
So if I subtract this 444 again,
it's now back to how it was before: 1234 and just 1.
So addition and subtraction is quite easy.
If you flip this switch the automatic clearing of the keyboard is no longer functioning,
so whatever you input it remains here.
Let me first clear this register.
To do that you have to lift up the carriage,
so that the register gets disconnected
from the main mechanism,
and then you can pull this clearing lever to the right.
The same for the counter.
So I've got 1234 in the input.
Suppose I want to multiply that by 76.
Well, first I'll do the six, so I'll turn the crank six times.
Now I'll shift the whole carriage to the right one step.
There's a knob on the left here to lift it up
and shift it to the right,
so that now we are on digit number two.
So this one in the counter that's going to be 7,
because I want to multiply about 76.
So I have to turn the crank seven times.
The counter now says 76,
the number I wanted to multiply by,
And the result is here - it's 93,784.
That's that's all fairly straightforward.
Division is it's similar to what you'd expect.
It's basically repeated subtraction.
You can enter a number actually by turning these knobs.
You do have to lift the carriage first,
then you can turn these knobs to any number you like.
And suppose I want to divide that by 12.
I've entered twelve - it says twelve here.
So dividing this by twelve you start by
shifting the carriage to the right
until your number lines up to the leftmost section of this,
because we're doing long division.
You have to subtract from the register,
but we do want to count upwards
on the counter normally,
so this one that says U for the Umdrehungszählwerk,
the revolution counter, that one stays in addition mode.
And this one, the one that says R for register or result,
that one goes into subtraction mode.
So now we're ready for the division.
So we just turn the crank
until this number that we have here
is no longer greater than 12, the one we're dividing by.
Then we shift the carriage,
and now subtract from here until it's under 12.
And shift the carriage one more time.
Now subtract again until we're under 12.
This number happened to divide exactly,
because we have zeros here,
and it was divided by 12 and the result was 374.
If it didn't divide exactly we'd have a remainder left here.
If you turn the crank once too often,
you go to a number that's below zero,
it overflows, and if you do that a bell rings.
That shows you that you've gone too far,
and then you have to swap these two,
turn again to restore it to how it should have been,
and swap these two levers back again.
That's a bit of a faff but yeah it works.
It helps if you keep track of this so you don't have to go
to that extra step of undoing your last turn of the crank.
So that was the division, and
so that's basically how this machine works.
It's very straightforward, but
it's not the most user-friendly machine.
Many variations of this model were made, as I said.
There's an electric one that has an electric motor here
and it has a column of keys that
tell you how often you want to  turn the crank
so if you press a 7 on that extra column
the electric motor would turn the crank 7 times.
Later models were more and more automatic.
They'd not only do fully automatic division
but also fully automatic multiplication.
They'd shift the carriage by itself.
It no longer needed to be lifted when it shifted.
And lots of improvements like that.
After the Second World War,
well Glashütte is in East Germany,
so what they did was,
Reinhold Pöthig transferred all the intellectual property,
the patent rights and so on, to his daughter.
And his daughter and son-in-law,
they left to West Germany, and eventually
he, this son-in-law, Ulrich Eichler,
he joined Diehl which was another company
that made mechanical items
but they hadn't made calculators before.
So Diehl began to make calculators in 1952
based on the Archimedes designs.
Reinhold Pöthig, he stayed behind in Glashütte,
Eventually the company became state-controlled,
and Reinhold was removed from the company.
He died in 1955.
This original Archimedes company in Glashütte,
that continued to make calculators for the Eastern Bloc.
They were unable to export those calculators
to the West because they didn't have those licenses,
didn't have the intellectual property rights.
But they made Archimedes type calculators
for the Eastern Bloc,
and they did so until about 1960, I think.
Eventually that company changed to an electronics
company and became part of Robotron
just like Mercedes Euclid did.
One more small thing.
Most of these Archimedes machines will
have more writing here.
It will at least say Glashütte and Reinhold Pöthig.
This one doesn't. I don't know why.
It may be that this was a special large order
for this Überlandwerk Glauchau,
which is fairly nearby Glashütte.
Maybe they did a special order of lots of machines and
they didn't need to have this logo and
company name on the front.
So that was the Archimedes Model D.
Thank you for watching!
