Those 42" mowers came out in the late 70s and disappeared by the mid 80s. We sold a few of them at our dealership. Luckily, we didn't sell many. They turned out to be a horrible piece of junk. I'm sure that after dealers sold a few of them they stopped ordering them, which most likely led to it's demise.
It doesn't look like it has the original engine to me. The original engine would have been white.
It's value would be what it would be worth parted out.