Counterfeit Carter M6866 mechanical fuel pumps being sold on Amazon. Buyer beware!

Most brands today are simply that - they stamp their brand on parts made by others. Especially true for brands from car manufacturers. Much discussed on a M-B forum since some people insist on paying $$$$ for M-B branded parts. Others find the source of those parts and buy the same part under another brand for sometimes 20% the price. On a Blue Moon, a Mopar branded part at the dealership may be the cheapest. In general manufacturer-branded parts are best, since they assure the quality even though they don't make them. Even Bendix has begun selling foreign parts under their name, but at least they use "Bendix Global" brand for those.

So, no proof that those two parts in post 1 are not both legitimate Carter brands. No expert, but the top one appears die-cast and the bottom one sand-cast. The top one appears better quality. What you can't tell is the quality of the rubber diaphragm inside. When that fails, gasoline can flood the crankcase to dilute the oil and perhaps damage the engine before you find the problem.