The Classic Machinery Network

Previously I had showed some Dresser 350 dumptrucks and a PC1000 at a minesite where I worked in the early 90s. That company lost the stripping contract and a new outfit moved in with a PC100 F/Shovel and a fleet of Cat 773s & 777s. Here is the F/S being assembled.

When was this series produced?
It looks rather old.