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Can't speak to actual difference in use, but in a parts search, the 1971247 appears to be applicable to mostly truck use with a wide range of Chev. passenger cars too, but no Corvette. The 1852722 appears to be similar in a wide use for trucks and various GM passenger cars including Corvette. Used on Corvettes from '58 to '74 on all engines except dual-4 barrels of the C1 era.
From what I remember as a kid, the black one was superceded by the other one. Just an educated guess. In the 70's, you never saw the black one anymore.
The captive screws kept you from dropping screws inside.
From: At my Bar drinking and wrenching in Lafayette Colorado
The black one is the heavy duty unit. The white one is a light-weight cheap replacement that came along once the word "performance" had been forgotten by the public.
The black heavy duty unit is available in a tan color under Echlin/NAPA part number RR1670. About $8.50. As you can see, it's the same, heavy duty molding and tab as the black heavy duty GM rotor shown above:
The "standard" unit is also available from Echlin/NAPA under part number RR169SB. About $4.50. You can see it's the same as the cheap Delco unit shown in the OP post above:
Use the HD stuff.
Lars
From back in my auto parts days, the tan unit is the same as the old Accel performance ignition parts, and if I remember right the ones stamped with an E were an emission rotor and were a little bit shorter than the standard ones, created a bigger spark to jump the increased gap, used to fire leaner F/A mixture, before the HEI came out. Then as usual this is now the only one available.
