I just got an NS calculator on eBay that looks exactly like your Hiradastechnika 1024. Once I clipped out the exceedingly dead 3-sub-AA NiCd pack, I powered it up with a regulated supply and it works perfectly, except for the third and fourth rows of buttons. Should be no problem to fix that.
What I really like about it is the LED display units. Each of the seven 'segments' is made up of tiny dots, and the numbers that should be rounded in the corners (3, 6, 8, 9, 0) actually look rounded, because the dot in the corner is left off for those numbers. Nice design.
If only they were a tad brighter...
Other than the keyboard and the (expected) defunct battery, mine is in great shape -- like yours, the chrome border on the plastic is not worn at all (probably because the power switch is on the side, not on top near the border), plus the carry case is near perfect.
I like the old ones because they're built on a not-too-microscopic scale where there's a chance I can fix whatever problems I'm most likely to find. I should take a screenshot of "For parts or not working" from an eBay listing and put it on a T-shirt. Some folks say that if you can't open it up and fix it yourself, you shouldn't buy it. That gets tougher every day. But it's really easy if you design and build your own (DIY5, for example)!
Dale