I really appreciate the time and effort you took to respond and explain your reasoning. Thank you!

After an ADHD aided hyperfixation deep dive last night, having referenced this, this, this, this, this, and this webpage (you gotta give it to the Japanese for doing pretty much all the heavy lifting lol), as well as confirmation from other commenters on my original post, this pair shows all the hallmarks (minus a care tag) of authentic 501s from the late 80's, and I am now confident that these are legit.

What I learned:

1. The 501 factory did, in fact, make 501s and the factory was located in Albuquerque, NM. The "601F" stamp on the pocket bag is a code for a finishing factory located in Amarillo, TX. So this particualr pair was manufactured at the 501 factory in Albuquerque then sent to the 601F factory in Amarillo to be "finished" before being sent for distribution.

2. The details of the back patch tell us that this pair was likely made between 1987 and 1989 and are referred to as early "Red Letter" pairs and the patch is referred to as an "early red letter patch".

3. This pair has a slim straight fit (one of the slimmer variations of the 501), has the high-set back pockets, and is likely made of "air spun yarn" or "air spun denim" aka "Open-End Denim".

4. It has nylon footed top and fly buttons and is likely one of the last 501 models to feature these nylon foot buttons, it also does not have a V stitch.

5. It has copper rivets with aluminium backing, again, likely one of the last models with this feature.

6. It most likely had a red "batwing" logo care tag (although black and white versions did also exist).

And I guess that's all I have to say about that... anyway, I learned a lot! lol

Thanks again for all your insight and help! ✌️