Some days ago, I’ve searched for early patents from Festo, that might give some more help with my device.
There are too many patents and several variants of the company name. I narrowed the search by year (mid 70s to early 80s), only patents with illustrations and some German descriptions. But found nothing much of interest.
The only notable early one is this with some good illustrations and instructions (best viewed usually the external links in PDF style)
US4070702A (German DE2713253A1)
I don’t remember how I found this from Allen Bradley. 8 bit CPU 8008 but I think 16 bit bus and programmed in octal (at least the addresses) and in bits. Very interesting. (But I think it’s so much different that it’s not much helpful).