Originally Posted by
Salamandrine
...I think the OP is asking about the mountain racks with the top plate in general...
Yes, that's what I took it to mean too, but Blackburn's MTN series of racks with the "load support platform" were available at least as early as 1984. Also, the platform was't used only the MTN racks. It was also on their Fastrak of the same period. IIRC, Rhode Gear's version was simply called the Rhode Rack.