This rear axle and the front axle came from under a 79 Cherokee I found in a salvage yard. The front axle BOM is 603685-6 (JEEP Model 44 FRONT 1978 - 1979 J10, J20, HONCHO, CHEROKEE WIDE TRACK)
I managed to find a tag attached and the build date, but no BOM.
I speculate that the tube has been replaced with Part number 70100 X built in May 12, 1980, but am unable to comfirm 70100 X as a part number for an service axle tube.
Entering 70100 X on Dana Expert part look up:

You Entered 70100X
Product: Light Axle
Status: Inactive
Description:
Drawing:

Entering 70100 X on Dana Bill of Materials returns nothing.
http://i819.photobucket.com/albums/zz115/krosati/003BOM.jpg

I am also confused as to the lack of a threaded bung in the diff cover, but rather a rubber plug as normally found on D35.

http://i819.photobucket.com/albums/zz115/krosati/001D44diffcover.jpg

Should the front and rear tags be the same number? Can I utilize this tag to verify anything other than the ratio of 3.54:1?
http://i819.photobucket.com/albums/zz115/krosati/002D44Tag.jpg

I'd like to ID this axle so as to obtain bearings and seals before tearing into it.

You can pull the cover & count the teeth on the ring gear. I would bet a wooden nickel that it has 3.54 gears. If you are going to build it I would also get a heavy duty cover. Is the diff offset?

Im not sure on your part # problem, but i Pulled a set of 44's out of a 79 cherokee for my zuk project. They did use a rubber plug on a paper thin diff cover for the rear.
Is the diff offset roughly 6" to the passenger side? It should be if its original.
It should also be about 2" narrower WMS to WMS than the front. They were that way originally on those too.
If that all sounds right then you should have a factory axle. Good luck

Edit: Just went out and verified that my rear has a bom of 603818. I have no idea what your # means.

Is the diff offset?
It has a passenger side pumpkin. The right tube is about 24" and the right is about 16" long (from the cast edge of the diff to the backing plateflange)
Is the diff offset roughly 6" to the passenger side? It should be if its original.
It should also be about 2" narrower WMS to WMS than the front. They were that way originally on those too.
If that all sounds right then you should have a factory axle. Good luck

Edit: Just went out and verified that my rear has a bom of 603818. I have no idea what your # means.

That's good news. I did some more research this evening and will measure the axle lengths to detemine the actual axle I have.

According to Dana Expert, the only difference in the jeep application D44 is the right axle lenghts. Seals, bearings, and such seem to be all the same.

Most bearings have numbers on the thin sides of them. You can always get the numbers from the bearings. The races have individual numbers on them.

Thanks for the info. I'll be diving into these in the next few days.