G'day folks,
I've moved these posts to their own thread in the Greenfield forum; I'll get the topic changed to something more informative.
Greetings shadow112, and a warm welcome to the ODK forums!

I suspect you have an uncommon variant of the HD8, with the electric start Robin engine; the first one we've seen here at ODK only surfaced recently - see PhippH's thread below.
As far as the earliest Greenfields go, from what I can work out, they had the single drive belt from the engine - I know that the later Red HD-8's had two. The wheel drive from the pulley closest to the crankcase, and the cutter drive belt on the hand clutch pulley outside that.
I've seen it suggested that the first models had a front axle mount that was different from both the Red and Yellow series HD-8's [which are easily distinguished], but nobody has come up with an example to prove that, one way or the other, so far.
I also need to add that the 'Tractor-x' [x= hp rating] series with vertical shaft engines were Briggs only until ~1979, when the Honda GV400 11hp engine first came out.