Frankenorange
Orange 🍊 Fan
Interesting. I was told that due to over production during that period (early 80’s) that Ribble used to buy frame Sets from European bike builders and paint and decal them and sell them. So I therefore assumed the whole frame set is Cinelli. I was told this by a person knowledgeable in this area.
Search Ribble SLX on this website and you will find examples with the Cinelli spoiler and maybe, somewhere on those pages, is the answer.