Just a quick follow up...
I found out on another forum that this is a model 80 AC plow...
The frame is unmodified...
The plate assembly from the snap coupler was utilized to make it into a 3 point conversion...
Someone fabricated the 3 point pins onto the lift bar while utilizing the plate assembly from the snap coupler...
Ken, you were correct on the fabrication...
AC did sell conversion kits for their plows and did sell some 3 point plows...
My father said that the 3 point started selling when the series 4 D-17's went factory 3 point...
I think that the series 3 could be ordered either snap coupler or 3 point...
I am not sure of the time frame but it would have to be mid 60's...