Originally Posted by Salamandrine

I've never seen a Blackburn mtn rack with double stays and an extra attachment point like that. Would have required an extra custom set of braze ons. This particular mutant rack appears to be from the 90's, probably to fit one of the mutant MTB frames of the era with a swinging rear triangle or something.

The standard mountain racks with a top plate like that came out in 1983, as best as I can recall. It was soon after the Stumpjumper and competitors came out. I sold a lot of them at my high school LBS job. It was definitely not the 90s.