Hi Oliver, there’s a fair amount of variation around the old 531 decals so it might well be a 531. Our official partners H Lloyd stock some of the old style decals, so you could take a look at the ones they offer ( https://h-lloyd-cycles.myshopify.com/collections/reynolds ) and see whether the one that’s on your bike is among them. Without having seen the decal however it is hard to tell. If you are keen to know more, feel free to email us a picture on toptubes@reynoldstechnology.biz. Kind regards

My bike might have a Reynolds 531 frame, but I am not sure, since the stickers have red, instead of green letters!!

You have any clue what that’s all about?

It’s a Puch bike probably from the late 70s

Bye,
Oliver