Where would I find the date codes on an alternator and how do I decifer them? Thanks in advance.

There are several dates to look at. The casting dates in the front and rear cases are cast into a wheel shaped circle divided into 12 pie shaped segements. In the center of the circle will be a 2 digit year (example 69 = 1969) These segments are either empty or have any number of raised bumps in them (actual bump count does not matter). The segments that have raised bumps denote a month marked off of the 12 month calender, for instance if there are 3 remaining empty segments (marked in blue) then the casting was done sometime in September of that year, in the case shown below it decodes as September of 1969. The front and rear dates usually matched but not always, seeing them a month or so different is not unusual.

Here's the casting date on the back of the same alternator

Here is the entire back of the alternator, notice the correct ribbed center bearing, most replacements are flat.

Assembly Date - 4 69

The part# and assembly date are stamped into this pad. Typically the date (closest # towards the engine) is the month and year of assembly

The diodes are also dated, they vary in date, they should always date on or before the final assembly date shown above. The first 3 digits are the day of the year and the last is the year, example, this one decodes at the 190th day of 1969. The individual dates were generally close but usually varied on the same alternator. The "M" stands for Motorola.

Anyone know what the top three numbers above the part number represent?

Not me Snoop, I'm recording a bunch of them though and trying to decode them, so far nothing is adding up that points to an answer

Maybe an inspector or assembler ID number.

Looking at the picture I posted, it appears that the three lines where stamped at the same time using a single three line stamp. Notice the alignment and spacing of all the numbers, both horizontally and vertically.

Yes, I have several realated hypothesis, I just haven't reached any solid conclusions yet.

It's to bad the numbers are stamped in such a hard to see location.
Maybe some of the other members can post some pictures, if we get enough maybe we can see a pattern?

Been working on this w/ a spreadsheet. Trying to get some decently firm ideas conc. casting dates as related to assembly dates and then diode dates as related to same. Most alternators we see have positive diode dates from the same lot and the negative will also be the same. There are others that have had wildly spread dates. As far as the top three stamped numbers my money is on shift, plant, and line. Thinking that somebody had to be accountable if a bunch of "duds" came back. Still trying to find what NW stands for on some of the alternator and starter castings. KCP = Kokomo Casting Plant and they came us with some real crap toward the end of the "roundback" era.