Complex sentence: Models were precisely crafted in a professional and uniform looking range... and for leftover selections of models already used elsewhere-that was something of a marvel in the late 1970s and early 1980s.
Split into simpler sentences: Models were precisely crafted in a professional and uniform looking range from leftover castings that had already been in use elsewhere. That was something of a marvel in the late 1970s and early 1980s.