This is on a 2 ton but same idea, the black plate is the clamp plate.
https://picasaweb.google.com/lh/photo/RFsNMIS9lBhbuIqC2lp0UdMTjNZETYmyPJy0liipFm0?feat=directlink

Also on a 2 ton, but this is an original one. The older ones like this use a flat lug nut (the nuts with the little slits in them are original Marsden nuts), the later/modern clamp plates use a beveled lug nut
https://picasaweb.google.com/lh/photo/SlJJGfds_gFZpL2YoQzTNdMTjNZETYmyPJy0liipFm0?feat=directlink

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-