Finally found the ladder. Wibe NOR-BAS. Here's a spare parts pdf with good drawings of the ladder and pulley system. Maybe there's hope of figuring it out now.
http://www.wibeladders.no/globalasse...parts-list.pdf
Edit: and here's even a video demonstrating how to use it. I love how you can look for something for months on the internet with no luck, and then suddenly you find that golden clue and everything turns up.
https://m.youtube.com/watch?v=LrFnRqdL4rU