It's actually all silk screened twill. The only leather is on the sleeves.
Are you talking about the actual jacket or the Etsy jacket? I know the actual jacket is twill. (I was actually the first one to point it out here as well I think, and with all the hundreds of hours of research I've done on it so far I'd be pretty dumb to miss that little detail.) But the jacket for sale on Etsy (shown in the post I quoted) is leather with snake print embossing. I've had enough snake print garments, leather and not, in my time to tell, haha. Not to mention the add even states it's 100% leather...
Also... back panel fabric:
Correct heavyweight twill/drill/bull denim specially dyed and bleached multiple times. Next comes the screen printing... have all the supplies, just need to find the time to do it.