The serial number is "garbled", for lack of a better word. The "J8466" at the end translates to September, 1984. "510" is the frame size in millimeters, measured from the center of the crank to the top of the seat tube. Right after the 510, there should be a letter, A through E, representing the length of the fork steerer tube. A 51cm frame would have an "A", which is the shortest steerer tube fork. There should be a "W" before the "J8466", and that means the frame was built at the Waterford facility.

So, if it followed the mid-eighties self-describing serial number convention, it would be 510 AW J8466. The frame would be the 66th Paramount built by Waterford in the month of September, 1984.

From the decals and the garbled serial number, I agree with Pastor Bob; it appears to be a 1985 model year Waterford Paramount "Standard", built in late 1984.

1985 Paramount catalog page 1

1985 Paramount catalog page 2