That jack has nothing in common with a Hein Werner nor Blackhawk. Its your typical Yasui designed Import but id say yours actually uses a Poly U-cup on the Main Ram. Go ahead and try Sears but "When" you fail give me a shout and ill hook you up.
Just for future reference the Green/White jacks that Sears sold in the 70's where also Yasui designed and hailed from Japan, They did sneak in a few SJ series Blackhawk jacks in during that time frame but the JAP units where by far the Most common.
* Hiball mumbles.. Yasui based on HW. wtf sdlkjalsdkfj crazy people...grr... rawrs..