I wonder if they could be Happijacs with parts removed. They look kinda like the Happijacs I see on Panther RV but the crank I see for sale there wouldn't work with yours. You might try sending your photos to Panther RV, Etrailer, and/or Happijac.
Also- I talked to my brother and the Sunlite he recently sold had round-legged tripod jacks-- the Riecos I believe. He also said his were mounted to plates that allowed them to be turned sideways for travel.