According to some info I got from AAPK that Dale Vincent (username orvet) put together, the SP7 was made from 1989 to 1991, with a retail price of $32.95. It's a handy, convenient knife, in my opinion, and worth the $12.00 you spent on it. I have the Craftsman version and paid around $20-25 for it when I bought it at Sears YEARS ago.
The cut through the tang stamp likely means it was rejected by quality control for some reason, and is a factory second. I don't even know if Schrade released factory seconds, or if they found their way out of the plant in lunchboxes, or some other way. I have several myself. Look it over good. From what I've seen on mine, you can usually barely see the problem, and it's generally always cosmetic.