The date of manufacture is stamped on the bb spindle.
You have a early 80's Raleigh (grand prix?) that has been ridden hard and put away wet.
They were made briefly in the states to meet demand from the 70's bike boom. The bike boom was over by then and the manufacturing was moved to malaysia.

Google search Raleigh history. There is a whole report on line that chronicles the history of the company.

If you are curious about value we sell those bikes for $100-125 overhauled and in good working condition.
Yard sale versions sell anywhere from $15 - 40 around here.

Enjoy