Jaap Scherphuis
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jaapsch.net
Jaap Scherphuis
@jaapsch.net
140 followers 200 following 250 posts
Mathematician, likes mechanical calculators, twisty puzzles, the Psion II, and tiling patterns. See https://www.jaapsch.net
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jaapsch.net
The ZX81/80 Print ‘N’ Plotter was a semi-transparent sheet that allowed you to trace pictures with pencil and pixelize them so that they can be approximately displayed on the Sinclair ZX81’s screen of 22x32 characters or 44x64 pixels. The sheet can be washed clean.
The ZX81/80 Print ‘N’ Plotter. As you can see, I was into maps
November 12, 2025 at 5:29 PM
Reposted by Jaap Scherphuis
chrisstaecker.bsky.social
New video: I went to see the Pascaline! They did not let me touch it.
youtu.be/CROrLQpN6dc
Pascal's 1630 Machine: The First Calculator! Pascaline Review / HowTo
YouTube video by Chris Staecker
youtu.be
October 24, 2025 at 11:38 AM
jaapsch.net
Recently I bought this toy calculator from 1971. It is quite clever how its 2-digit register is shown not just as digits but also with columns of coloured dots.
A toy calculator, made from yellow plastic, with a rotary dial for entering numbers, a two-digit accumulator register on the left, and a counter register on the right. The register show the value 69. Below that are two vertical rectangular windows showing a column of 6 dots and a column of 9 dots. The finger is in the rotary dial at the number 2, and about to turn it. The finger has hit the stop after dialling in the number 2. The register now shows 71, with the windows below it showing a column of 7 dots and a column with 1 dot. This is the *original* box. It is called the Minirechner 99, made by Schildkröt.
October 22, 2025 at 8:55 PM
jaapsch.net
On an auction site someone is claiming to have a Comptometer for sale, but the picture is some kind of AI-generated rubbish. I don't see the point, but it makes for a fun game: How many errors can you spot?
Not a real Comptometer. How many errors can you spot?
October 12, 2025 at 10:53 PM
jaapsch.net
This little guy is the Facit Wizard. It is the advertising mascot for the Facit mechanical calculators. His first appearance was in the 1950s.
1/3
Facit Wizard figurine, facing left with his arm outstretched. A Facit Wizard figurine, body turned to the right, head turned towards the camera, and arm down. The 2 Euro coin is for scale.
September 28, 2025 at 4:04 PM
jaapsch.net
Today I opened a box from my storage unit and pulled out six Contex B adding machines. These were in production from 1951 till about 1970.
Six Contex B adding machines. The front two are for British currency (pounds, shillings, pence), the middle two are for ordinary decimal additions, the back left one is British currency with farthings (quarter pence), the back right one is decimal but with a halves column. The underside of the six Contex B adding machines, showing their serial numbers and list of patents. The original rubber feet deteriorate with age, so they are often missing or replaced.
September 21, 2025 at 8:58 PM
Reposted by Jaap Scherphuis
pixelhart.bsky.social
Picket Right, a font that's only 2px wide

Pixel art done by trampolinebears at r/PixelArt.
#pixelart #pixel #art #indiedev
Image made by trampolinebears
September 9, 2025 at 10:05 PM
jaapsch.net
I went to a large car boot sale today and found several calculators. Here are some pictures. I only bought the Odhner in the last picture, since I already had the others in my collection.
Two similar Brunsviga pinwheel calculators - one an older black Nova II, the other a later 13RK. A Burroughs Calculator, i.e. a class 5. It seemed to work fine except that the clearing lever was not connected properly. Another pinwheel calculator, an Original Odhner 129. It was completely stuck, halfway through a back transfer operation. I bought this and quickly managed to get it all working, but it will need some more cleaning.
September 7, 2025 at 3:17 PM
jaapsch.net
It's been a while since my last calculator collection update, and this time it's not even a calculator.
A gorgeous Schäffer & Budenberg revolution counter in a lined box. A close-up of the 4-digit revolution counter. On the face says "The Schäffer & Budenberg Manufacturing Company, New-York-Brooklyn, German manufacture". Underneath it has a small drawing of a pressure gauge, in the middle of the work Trademark.
August 10, 2025 at 8:09 AM
jaapsch.net
Yet again Stephen Freeborn shows off some amazingly weird early adding machine

youtube.com/watch?v=8tvE...
Centigraph adding machine
YouTube video by Stephen Freeborn
youtube.com
July 18, 2025 at 5:17 PM
Reposted by Jaap Scherphuis
ramiismail.com
Bye forever, WeTransfer.
WeTransfer TOS says they can use all your uploaded content for genAI
July 14, 2025 at 11:57 PM
jaapsch.net
I’d never heard of chisanbop, but it was a pleasure to watch this feature-length documentary in one sitting. A fascinating and well-told story of a forgotten subject.
chrisstaecker.bsky.social Chris Staecker @chrisstaecker.bsky.social · Jul 6
My most ambitious video project ever.

The story touches on lots of big themes and for me is genuinely thought-provoking in many ways. And it's a story that I don't think has ever been told before. I hope other people will find it interesting too. #chisanbop
youtu.be/Rsaf4ncxlyA?...
The Rise and Fall of Chisanbop
YouTube video by Chris Staecker
youtu.be
July 6, 2025 at 10:12 AM
jaapsch.net
When a regular hexagon tiles the plane, each tile has 6 neighbours. In other tilings by a convex monotile, you can have more neighbours on some tiles by having others with less. The red tiles here have 8 neighbours. There is no upper bound, as you can simply use narrower strips to get more... (1/2)
A tiling made of squares, each subdivided into five parallel rectangles. The orientation of these square subdivisions alternate horizontal and vertical. The red rectangle tiles (the outer rectangles of each square) have 8 neighbouring tiles, though all the others have just 4.
June 24, 2025 at 8:43 AM
jaapsch.net
Here are some pictures I just took of a small barred grass snake in the fish pond in the back garden.
A barred grass snake sitting on a lily pad in the pond of our back garden. Another view of the barred grass snake sitting on a lily pad in the pond of our back garden. It now has its neck partially in the water.
June 11, 2025 at 3:03 PM
jaapsch.net
Now it's time for a video about an adding listing machine, the Dixi. It is basically the same as an Addo-X, just painted brown and with a Dalton-style keyboard layout. This one is a model A from the 1940s.

www.youtube.com/watch?v=r5YB...
The Dixi adding machine
YouTube video by Jaap Scherphuis
www.youtube.com
June 7, 2025 at 7:10 PM
jaapsch.net
The latest addition to my calculator collection is an early Britannic, made by Guy's Calculating Machines Ltd in about 1930. This was the only pinwheel machine made in Britain. It started small, with only 2000 units made in the first 15 years, of which this is one.

www.youtube.com/watch?v=hwqE...
The Britannic calculator by Guy's Calculating Machines
YouTube video by Jaap Scherphuis
www.youtube.com
May 29, 2025 at 6:58 AM
jaapsch.net
I've been working on another old mechanical calculator and had some trouble reading the serial number on the back. I wonder if it was the last one done before the weekend, or the first one the Monday morning after.
A serial number struck into the back plate of an old mechanical calculator. It says 1462, but the 4 is turned 90 degrees, and the 2 was first struck upside down and then only partially struck the right way up.
May 26, 2025 at 9:13 PM
jaapsch.net
Here's the video of my wood Comptometer, a mechanical calculator from about 1902.

youtu.be/cXQF6svDqKU
A wooden Comptometer
YouTube video by Jaap Scherphuis
youtu.be
May 9, 2025 at 10:17 AM
jaapsch.net
I've been fixing up this lovely old mechanical calculator, a wooden Comptometer made in about 1902. Tomorrow I'll put it on my website and post a video.
A wood-cased Comptometer, a mechanical calculator from about 1902.
May 8, 2025 at 8:30 AM
jaapsch.net
My latest calculator video is a short one about another Multo model 3. As with nearly every Multo you find, it was completely seized up from dried oil when I got it, so it took a lot of effort to get it running again.

youtu.be/JgRDggPHek0
The Multo model 3 calculator, version 2
YouTube video by Jaap Scherphuis
youtu.be
April 25, 2025 at 5:02 PM
jaapsch.net
I bought this booklet just for the one hilarious photo. It is a report on the testing of a "vaudeville telepathist". Josef Kraus was a Czech who took the stage name (Frederick) Marion, and one of his tricks was to have someone hide an object, then he would hold their hand and find it. (1/2)
Preliminary Studies of a Vaudeville Telepathist, by the University of London Council for Psychical Investigation. Published in 1937. Photo of Marion (born Josef Kraus), a mentalist in the 1920s and 30s. Here he is "psychometrising a letter", finding out the contents without opening it.
April 19, 2025 at 5:13 PM
jaapsch.net
Poor little useless switch
Light switch, with a label above it with the text “No function”.
April 15, 2025 at 8:53 AM
jaapsch.net
A beautiful morning 18 months ago
Morning on a lake in Norway, a little North of Rjukan, taken on a holiday in September 2023.
April 11, 2025 at 11:45 PM
jaapsch.net
Here is a nice tiling pattern found in the wild. It is a photo I took in 2023 of a partitioning screen inside the Blue Mosque in Istanbul.
Photo of a tiling pattern used in a partitioning inside the Blue Mosque in Istanbul.
April 8, 2025 at 7:29 PM
jaapsch.net
The ads for science toys in the 1930s were awesome. Case in point: The Radium Spinthariscope.
"Witness The Destruction Of Thousands Of Worlds"
I'd buy that for a dollar.
Ad from 1938 for The Radium Spinthariscope, a toy version of a scientific instrument that makes visible the radioactive decay of radium atoms. "Witness The Destruction Of Thousands Of Worlds" It cost just one dollar.
March 31, 2025 at 9:07 PM