The dash 2 model 66 was made between early 1982 and late 1985. The engineering changes in the -2 is the elimination of the pinned barrel and recessed cylinder and has a slightly lengthen cylinder Vs. earlier models variations.
Yours also have the flash chrome target hammer & trigger which is a nice feature.
I would say that your M66-2 is worth about $650 and $50-$75 more if you have the factory labeled box with papers and tools.