I have recently acquired this machine. It is a twin rotor/blade hover mower with 2 drive wheels and a 5 speed gearbox. The 5hp Briggs and Stratton Industrial engine is from 1990, according to the code stamped on its side. I can find very little information on this mower, but there is a copy of a poster showing it which supposedly dates from the 60s. On the poster, it has a sulky (seat on wheels). I have found an advert and some parts drawings for a GCL75, which was very similar but had safety features such as deadman's handle and ability to engage and disengage the blade drive from the "driving position".