don gate

I need help with the age and value of a casino that I purchased in 1980

I bought an Epiphone casino (sunburst red and gold) in 1980 and I would like to know what year it is and its value. I would like to sell the guitar. No. 810258 style E230T (there is a hand written D after the T The label states “union made” “Kalamazoo Michigan” Thank you for your help