Hart Parr isn't the first gasoline traction engine.  The Froehlich I believe was which later became the Waterloo Boy.  But Hart Parr did coin the name "tractor".  None the less I love those green machines.  I have an 18-28, Hart Parr 70, and a 28-44.  Am looking to add the 18-27 someday so I have all the Oliver Hart Parrs.  I also have an Oliver 80 and 2 Cockshutt 99's made by Oliver.  I would eventually like to get all the Oliver made Cockshutts.  Happy collecting!!!