Hot Pies
When I started, the office girls used 'Comptometers', large mechanical adding machines. Then the more senior girls were given Marchants (which could multiply) but had a huge moving register, and were very noisy on steel desks. So the factory sent up thick felt pads to put them on, very much a status symbol. Finally the supervisor was given a big electronic machine, with a splendid row of Nixie tubes along the top (and probably thermionics inside). But she could not be persuaded to dispense with her precious felt pad. The result was a lovely warm calculator - we worked out that if you put cold pies on the plastic top when the morning tea-trolley came round, they would be ready by lunchtime.