Lets take a look at some pre-electronic arcade games.
If you said one-armed-bandits and slot machines you are half right. Because mechanical based arcade games machines shared the floor with the more long-lived pin-ball machines and bandits from far before even I was born.
These arcade games machines were all initially very much mechanical based.
I’ve read first-hand accounts from the people responsible for building these machines and it appears that, towards the end of their run at least, the building process became more of a suck-it-and-see ‘black art’ than a precise science. Many of the people responsible for fixing these electromechanical marvels would freely admit to ‘not know exactly how or why they worked in the way they did half the time.’ The ‘science’ of these machines had evolved into an ‘art’ in much the same way early bedroom-coders would later forge the beginnings of the multibillion dollar/pound video-game industry.
One of the most collectable of these is the ‘World Series’ game released by Rockola in 1937.
This was pretty much a mechanical device, but did have some minimal electricity-run components, so technically this was an early electro-mechanical gaming device.