I bought it from a lady in Virginia in 2010. She said she bought it used back in the early 80s. She thought it was an MB250 due to the body's round chrome piece. It doesn't resemble either the MB250 or the MB200.
I can find no serial number.
I have also done some more investigative work and find that other than the neck it does resemble the 1970s EB-98. Not an exact match. During some periods the Masterbuilt was spelled Masterbilt.
If it was indeed made in the early 1980's, it was from the period that Epiphone [and Gibson] were owned by Norlin. It is pretty likely that your banjo was made in Korea. I can't help with the model number.
Imported Epiphone instruments have changed in specifications so many times that it's not easy to keep track of all of the variations, and I don't know of any book or website that offers a comprehensive run-down of them.
Other than it was made in Japan (1970s to early '80s) or Korea, (late '80s into the '90s) not that much we will know without a few more pictures — other than this is not a USA made Epiphone.
Remove the thumb screws holding the resonator on and take pictures of the back and inside. Try to get a good shot of where the plastic head meets the metal tone ring on top of the wooden rim and we will know more.