I've got six of their blades, including two from the 1980's. My experience is they take a very nice edge but will require frequent re-honing/stropping/steeling with use. The oldest blade, now about 30, has a few scattered pits.
They state they are "carbon steel," but that covers a wide range of alloys. They have a stainless paring knife, which I tried and could never get a good edge, plus this is not a correct knife for an 18/19th century re-enactor.
Mine have acquired a nice patina, a dark gray-brown and a bit uneven. The blades are quite thin and very good in the camp kitchen for slicing onions, carrots, potatoes, and corn-off-the-cob. I've had some that I kept in veg tanned sheaths that showed rust spots, for which I fault myself for keeping them there without oiling.
I'd be reluctant to sharpen one on a grinding wheel, as they are so thin and liable to overheat and loose the temper. A belt grinder is a bit more gentle, but a stone, oil, and patience are best.