Wow - thanks for the responses. I called my sister and asked her to call her sister-in-law to get detalis on it. I still think it has to be from the 80's - but still don't know what it is for.
As for the screws and nails, I checked my grandmother's china hutch, thinking that back then they didn't have screws (what do I know) - but sure enough, it has the exact square headed screws (and same nails) as my table. She was born in 1902, got married when she was about 15 or so, and got the dining set a couple of years later, making it from around 1920.
The screws on the hutch are not buried deep - they are flush - but they look like the holes were pre-made with a tool -they definitely had woodworking tools back then - learn something new everyday. The stain is only on the main parts of the wood, not underneath. I know her dining set is solid oak, but still not sure what my table is made from. Don't think it is plywood, but could be.
Will let you know what I find out - hopefully this weekend.