I'll guess that it's late 70's, perhaps 1977/1978. Could be as high as an EG700. I can't make out the side detail, but I suspect that, with the three piece top, it's a pancake body.
What's it worth? What will somebody pay for it? It's not highly desirable, but that doesn't make it a bad guitar. Someone will pay $700-$900 USD, and perhaps a bit more; but, only the marketplace can establish value.