Note that sample I posted is painted black. It has a label on it that says "Bendix remanufactured" on it, but the flange and outlet areas look virgin, the part has never been installed on a car, so not sure how it ended up getting labeled remanufactured.
For Bendix master cylinders from the 60s and 70s their original finish is something I've never 100% nailed down. '67-'70 Mopar disc brake master cylinders were always painted black. Many NOS Mopar master cylinders from the '70s had sort of a parkerized gray coating. I've seen others where the body was E coated.
Bendix master cylinders I've seen from those eras for the other 2/3rds of the big 3 generally had black e coated bodies and plated caps.
I have a couple NOS Mopar late 60s with the bolt on cap drum brake master cylinders that have black e coated bodies with plated caps. I hesitate to mention that, as I was shouted down here several years ago for questioning if any of these with the E coated castings were installed on the assembly line. People were sure that never happened, that style master was always bare metal. They must have E coated ones used for replacement parts so they wouldn't rust when in inventory was the theory as to how they exist.
I was involved in a project at Raybestos around 12 or 13 years ago where we came out with a "premium" line of wheel cylinders, and one of the enhancements was that we black E coated the castings. That turned out to be a real headache, all the work setting up a complete second set of bills of materials, keeping otherwise identical wheel assemblies isolated from each other, and the added cost of the e coating, doomed the project and it was abandoned within a year. The fact that I don't think we were fooling customers much that a shiny black wheel cylinder with a higher grade of plating on the bleeder screw was worth paying more for than what our standard wheel cylinders cost!
If they wanted to keep replacement drum brake master cylinders from rusting while on the parts dealers shelves, I would think they would have painted them, not E coated them. That is why I wonder if any originally installed drum brake Mopar masters were E coated black.
Sorry to go a little off topic on the subject of original finishes! One of the few things about Mopar master cylinders I don't feel like I am an expert on.
