Help with identifying upholstery

Hi FABO!

I have a -65 Dart GT and the upholstery in it is not according to stock, so it has been changed some time in the past. Based on the pictures of the rear seat underside, it looks like it may have been at least a couple of decades ago.

However, I have not been able to identify what kind of upholstery it is. It kind of looks like -65 Signet seats, but with vertical lines instead of horizontal.

Can anyone here tell me what it is? Is it from another Mopar, or is it after market / custom?

Cheers!