The consensus seems to be that this version emerged in August 1961 following the Nivocode cap that appeared on the earliest of cars. This version was used until being replaced by the white Sovy cap in approximately July of 1962. During this period, the black caps did not yet have a patent number on the face. Also note that the aluminum float cover on the black Sovy cap has four equal sized holes – two near the bottom and two near the top. The later, white caps also have four holes, but the upper holes are closer to the top and of a smaller diameter than the lower holes. This unit has the proper float cover.
Application: Jaguar E-Type Series 1 3.8; Early cars between August 1961 and July 1962.