Welcome to the forum and congrats on the nice M66.
The SCSW says there was a M66 PC .357 magnum "F Comp" with some reported with the PCP serial prefix. It says they came with a 3" full lug barrel, dovetailed tritium dot front sight with adjustable rear sight, tuned action, round butt frame with Uncle Mike's rubber boot grips, counter bored 6 shot fluted cylinder and contoured cylinder release.. There was approximately 300 made and they were introduced in 1993.
Does this sound like your's?
Let me add, the book says suggested retail was $740 and it would probably sell for more than that now. You got a great deal.