It's not mentioned in the article (too obvious?), but for wondering: Seems like those computers where used by the sports manufacturer Puma (https://en.wikipedia.org/wiki/Puma_(brand))
But looking at the pictures of part 3 I have to conclude that the electrical installation was certainly not done professionally. In fact: the mains wiring wouldn't even pass inspection by German law.
So tinkerer or not, I doubt this was the place where this multi-million machine (in Deutsche Marks, that is) would have been installed originally.
[1] https://ibms360.co.uk/wp-content/uploads/2020/05/DSC_0062-10...
Additionally Puma was founded very close by and most likely the company was renting out / buying some office space for the accounting division.
That linked with the logo would make sense.