I found on ebay some magnetic stripe paper cards, 5x18.8 cm looking like this
I was curious for what machines they were and soon found it: Robotron K1000 desktop calculator series (K1002+3). More about that in upcoming thread part 2.
I first found Diehl alphatronic. (Diehl and the alphatronic brand was sold to Triumph-Adler in 1978).
The first German programmable calculator was the Diehl combitron (1966).
The alphatronic was green and had 160 registers for 1600 instructions.
Someone can attach many different peripherals (4 at a time):
2 magnetic tape cassettes
2 magnetic card devices
1 mark sense card reader
2 floppy disks 8"
2 ROM cartridges for maths or stats
paper tape reader
and a plotter
(see the brochure here)
CALCUSEUM DIEHL CALCULATING SYSTEMS: Alphatronic
The certatronic was enhanced and orange (1974). The alphatronic DS 200/300/400 were grey. All with green, grey and white keys.
One photo with a DS400 + 8" Floppy is on pinterest. Hi-res photos of inside and ROM modules are on catawiki.
A photo of a magnetic card reader is on the brochure, card inserted vertically. I found a tiny photo with a card inserted horiziontally, but I think that is the mark sense reader.