In my experience, around 1980 all hydraulic jack manufacturing went to china. all north American manufacturers closed up shop. or have the units made in china and rebranded. In china a requirement for size and lifting capacity is met but the units may change slightly from factory to factory, so repair parts won't fit. That's why they are sold by the pound. when imported. Also a big shop overhead can be around $500 per hour and every sales man/ mechanic has to sell $120 per hour. So an old jack with low tonnage is scrap.