Since most frames were built to order details like mudguard eyes and various other attachments were decided by the future owner of the frame. Colour schemes could be chosen over the entire model range.
mmm .... not how I remember it in the uk, when gazelle made a big appearance. They were very much stock frames in stock colours imported by sid and sold through his rotherham shop. The publicity machine was the paragon RT, arguably the best uk amateur outfit of the 80's and for a short while gazelle were a big competitor to Raleigh.
So the question is were they custom built or stock, and was the uk different to mainland europe?
It's very well possible that the UK importer had a different line regarding pricing and custom vs stock frames. I talk about the situation in the Netherlands during the hey-days of Gazelle. (Although there were regional differences in the Netehrlands.)