Garry:
Off hand, I can't think of any 15" with caps, at least on this side of the pond. The 126s switched to alloys in the late '70s, all 14s, only exception being the 6.9 that came with 15" bundts. 123s were all 14". 107s switched to 15" with the 560sl in '86, alloys only, maybe I'm forgetting something?
Rick