I saw a H-8 on eBay tonight. What year were these made? What could one do with it? From the photo it has a 16 key keypad, numbers 1-9 and the math symbols, decimal point, and 2 others i can't make out. What are those 2 keys? I'm not trying to buy it, I wouldn't know what to do with it even if i did. just curious. TIA.