Thank you very much; I have contacted him for a quote. I think many of the early engines may have used this size or even larger. I have some which may be Marklin-supplied originals which are nearly 3mm. Wilesco's common 2mm belts are too small for the larger Marklin lineshaft pulleys and accessories although I'm sure they will work with a lot of tension on the springs. For the past year I've been restoring a Marklin 4283 machine shop and I have to replace some of its 13 spring belts. This project is nearly finished so more to come soon.