That's an early generation 5.0 ci antivibe model. They used many different paint (color) schemes during those years, so I'd have to look at it a little deeper to get a positive identification. But I'm sure it's either a Super Pro (SP) 80, SP 81 or Pro-Mac (PM) 850. Later generations of this same saw (which I'm sure the one pictured is not) are the PM 800, PM 805, Double Eagle 80, and the 8200. This was a very successful design for McCulloch which they used in all of the versions stated from the middle seventies until they went out of business in the early nineties. These models were never as popular as the 10-10 series because they weren't marketed as homeowner (firewood) saws, but were sold to loggers who demanded a lightweight, powerful, and dependable saw. These saws filled that role beautifully for over 15 years.