This dark green color was first introduced in 1979. In 1981, the change to using wooden bowl handles meant this color was only produced for two years as a metal bowl handle model.
I recently acquired this one from long time WKC member landgraftj. He came into possession of it soon after joining the WKC in 2012. The original two rivet handle appears to have been repaired somewhere along the line. Landgraftj tells me it was like this when he acquired it. The nuts are recessed into the bottom section of the handle.
The legs have sections of copper tubing inside. Landgraftj tells me the legs also were like this when he got it. This modification was apparently an old school WKC solution to solving loose legs in the bowl sockets.
Although there may be more undeclared examples, I am aware of only a handful of these 18″ green MBHs in the WKC.