I checked out the Trip Machine website - apparently it's a secret!
They're made in Rajastan in Northwestern India, usually from good tough-wearing goat leather, 'cause you know,
sacred cows. Handmade leather goods are kind of a traditional Rajasthani thing, like rug making in Bukhara or cheesesteaks in Philly. They call it and their homespun style "Jawaja", which you can Google.
I can also tell you that the panniers being sold by our esteemed Madman's sponsor are actually a pretty fair price, even compared to buying direct from Rajasthan. So, if you like 'em, I'd go with that sponsor. My hunch is you'd also be far more likely to be getting "1st Quality" gear that way. No maker's gonna risk pissing off his or her "American distributor" by sending them the 3rd rate stuff made by Blind Ramesh after a bender.
Leather wears surprisingly well on a bike. If my "Military" didn't already have nice metal panniers, I'd be buying those.