Over the years i have had a number of calculators so i thought i would put on record the ones i still have.
This is a 'Memory Master X' which was purchased via mail order in December 1975 from a company called 'Shoportunities'. It worked well for a year or so and then started to go a bit iffy. The keyboard de-bounce seemed to fail and pressing a key may result in one or more numbers being displayed.
This is a Sinclair Oxford 100. I purchased this in 1978 in Browns Radio (now closed) on The Bridges in Edinburgh. The calculator was sold as a 'brand new surplus' item. This model was originally sold in 1973-74. I paid £1.50 for the calculator at the time.
This is a Commodore P50 programmable calculator which i purchased at the now defunct Comet in Dalry, Edinburgh in 1979. It was powered by a 9V PP3 battery which lasted much longer than i expected it would.
This is a Casio fx-3600P programmable calculator. I purchased this in the Students Union shop in 1983. For some strange reason i never felt comfortable using it because i did not want to damage the plastic wallet so it was carried around in its original cardboard box until it fell to bits. It is powered by a 3V coin cell battery. I think it is only on it's third battery since 1983!
The display was seven segment LED and the calculator was powered by 3xAA batteries. I still have all the original packaging, documents, manuals and the sales receipt.
The display did not have leading zero suppression so when for example the '9' key was pressed the display read '00000009'. The calculator was powered from a 9V PP3 battery and due to the heavy display usage i had to remember to switch it off when not in use.
I made my first faltering steps writing simple programs to solve repetitive calculations using this calculator. Commodore made the PET series of personal computers and later went on to make the VIC20, Commodore64 and Amiga. A friend of mine spent many hours using this to write and play 'Moon Landing' games....i never quite 'got' what he was doing.
This is a Casio SL-760lu credit card sized calculator. I purchased this in the early to mid 1990's but i have no recollection where. I know it was sold in a plastic bubble pack stuck to cardboard and i think it cost £6.99. It is powered by the solar cell only.