Just wanted to drop in and say that it's nice to see the machines still being played.
I used to work as a software developer/designer back in the late 1980's and early 1990's of fruit machines for a couple of companies located in South Wales.
Most of my design work was done for JPM and Ace. Did a brief bit of work for Crystal (later bought by JPM I think?).
Started out writing the games in straight assembly language (different languages depending on the CPU in the machine). Later built my own fruit machine game maker for the Atari ST that let me do all the light sequences, PAR tables, mathematics and simulation, and feature set of nudges, and accumulators, and so on, using a mouse and menu system instead of laboriously typing everything in by hand into text files.