The Massey-Harris GP 4wd was offered from 1930-1938. The GP was originally produced by the Wallis the tractor line owned by the Case Plow Company (The Case Plow Company was a separate company from J.I Case). In 1928 Massey-Harris acquired the Wallis tractor line to ad tractors to its successful implement business. In 1930 Massey-Harris introduced the GP 4wd to enter the row crop market. The GP was powered by a 226 cubic-inch 4 cylinder Hercules engine. With tread widths of 48, 56, 60, 66 and 76 inches the GP was a true row cropper. The GP 4wd is viewed as the first true 4wd tractor. It does not articulate or have 4 way steering like the modern 4wds. The GP is steered with right and left side breaking, which allows for short turns. http://www.bigtractorpower.com/masseyferguson4wdhistory.htm
Thanks to MC for showing me this unusual tractor, how incredible to run across this, and the REO school bus in the same day!http://www.massey-harris.com/
http://www.antiquefarming.com/masseyferguson.html
And for stats, facts, specs etc without photos but full of info http://www.tractordata.com/farm-tractors/tractor-brands/masseyharris/masseyharris-tractors.html