Interesting yes, but I don't think it is worth anything close to $800. Appears some parts are missing. Where's the rest of the pitch adjustment? Nicely repainted though!
Looks like it's all there to me. Uses Curvic couplings/face splines to index pitch and angle. Turn the lever to release axial clamp load via a tie bolt, turn to desired angle and retighten lever. No tools required. Lever between lower hitch pins operates pitch and lever on elbow operates angle. Sweet design. Looks like the blade can be offsett using those unused Curvics on either side of the blade. Or two gauge wheels could be mounted to them. The more I look at it the more I like it.
My old ARPS utility blade is worn at all of the pivot points. It looks like the only thing that can wear on this blade is the cutting edge, and that can be replaced.
I would pay the gentleman most of $800,[$700? make him an offer]for a rear blade that looks like it could last a long, long time and work well to boot.
They don't make them like that anymore. Lots of work went into blade. I wonder what it would cost today to make? Probably more than what people would be willing to pay.