It can be a bit tough to see in the photos, but the metallic green has faded and flaked to a sickly greenish grey in many places so it's not looking so hot. The decals are also pretty scraped up. Since I took the time to recreate the decals carefully, I will probably repaint it/have it repainted in the same colour, which I've Pantone matched (same goes for all decals). Also, there's a lot of surface rust (nothing more serious though) so I'd like to strip it down, go at the rust with WD40 and a steel brush, and then wash it and galvanise it with a self-etching primer for protection. The goal is to look exactly like the original, but not 40 years old.

To everyone else: Thank you so much for your insights! I have also spoken to the Jan Janssen shop about IDing it since they were very excited/willing to check it out, so hopefully the puzzle comes together from two sides.