The hemi cars used a unique and valuable Bendix booster and master cylinder. Both carryovers from 1970 and both painted black.
Some 71 non hemi E bodies got the carryover from 1970 model year standard Bendix boosters, which are black. But most seem to have the Midland Ross booster which is plated. I’ve never seen a Midland Ross painted black, so the one on eBay must have had a rattle can paint job done in it at some point.
1971 is a very interesting year for E bodies because many things changed on them over the course of the production year. Some things like the changeover of the 340 engine from one plant that painted them orange, to a different plant that painted them blue, are well documented. Others like the booster are more of a mystery, 2 manufacturers were used, but was there a definite transition time on the line, or were both installed concurrently for a time?