Master Cylinder Side Stamping

[Blowout]

I was doing some research on my 1970 R/T and so far it seems most of my brake set up is original to the car.  The master looks like the "171" style, but I haven't taken it off to be 100% accurate.  However, on the side of the master, I can read "9175C  8284C" in one single line.  I've done some research on the forum for date stamps and found some old stuff dating back in 2018 that confused me.  Some examples of date stamps have two lines, and then I found one just like mine with same numbers that the member had in an old Raybestos box.  Anyone have any feedback they can provide on this or tell me why mine reads this way?  Car has a SPD of 10/1969.

[mtull]

The date stamp should be on the next line under  "9175C  8284C".  If I recall correctly, other forum members have stated the aforementioned numbers are thought to be for internal vendor use?

The date format is: Y DDD. Example: 9 225, which is the 225th day of 1969 (August 13).

[JH27N0B]

Here is an example with stamping on the side of a "2229171" casting number E body master.  The 9175 and other numbers on the top row aren't the date code.  The second line is the date code of assembly.  In this case "0 100" which would be 100th day of 1970
The stamped numbers can be hard to see on a "well seasoned" original master cylinder that has been on a car 50+ years or taken off a car it was originally on, due to surface rusting.
Sometimes they will be easier to see after a good media blasting.
Back in the day aftermarket brake companies would often purchase OEM parts to box in their boxes, if projected sales weren't high enough to justify tooling up to manufacture their own version that fit and functioned.  Being a one year only part for one model line, if you find a NORS master cylinder in a Wagner, Raybestos or EIS box for a 70 E body disc, it would actually be an NOS Bendix part!
I used to find a lot of NOS Mopar master cylinders this way listed on ebay years ago, until word got out and people learned how to spot NOS parts in aftermarket boxes.

[Blowout]

@mtull & @JH27N0B thank you for the replies.  Very helpful.  I'll have to keep an eye for this when I restore the master cylinder.  Speaking of that, any kits out there recommended for that rebuild?  Probably mentioned in other posts, but just came to mind. Thanks guys.

[mtull]

I'm not sure.  I've been meaning to set aside some time to research.

Here's a few threads discussing rebuild kits for the 171
https://forum.e-bodies.org/wheels-tires-brakes-suspension-and-steering/12/kit-used-on-2229171-master-cylinders-discontinued/10767/
https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2653726/all/70-ebody-master-cly-repair-kit.html

[JH27N0B]

Best advice I have is to talk to Brad at Brake and Equipment Warehouse in Minnesota.  They rebuild vintage master cylinders and are very knowledgeable on the subject.
Many aftermarket master cylinder kits have been discontinued in recent years.  I assume Brake and Equipment has been able to find sources for the parts to use to restore them.
But at least as far as kits you can buy at NAPA or Rock Auto to rebuild vintage Mopar master cylinders, they are no longer made as far as I know.
Raybestos MK551 had the correct 1" seals to use to rebuild the pistons used in 2229171 master cylinders, but sadly is no longer made.