With the right lens design coating is irrelevant for photography. I used to harvest lenses from Folding Pocket Kodaks to try out on my 2x3 Graphics. I picked only Zeiss Kodak Anastigmats (all Tessars) and Zeiss Tessars. All shot beautifully on E-6 films. I have a couple of pre-WW I Zeiss Tessar. All very usable.
OP, if you want a pocketable 6x6 or 6x9 folder just look for one in good order, shutter especially, with a tessar type lens.
This is not to denigrate coating, single or multi-. It is invaluable for, e.g., zoom lenses where it reduces but doesn't always eliminate flare and improves transmission. I had a Beaulieu 4008ZM S8 camera with an Angenieux 8x8b lens. 8-64/1.9. Single coated. It t/stopped around t/3.3.