ok ,anyone know anything about David Bradley side delivery hay rakes?

Model # 917-5723, it is draw type, has 2 foward wheels ground driven, 2 rear swivel wheels, and a crank screw on same side as ground drive box wheel up on bearing area for thrasher wheel, plus height adjusters that are operable from draw tongue. its complete all there, are they a good rake? and what is adjuster screw for? looks to me like it moves rake bars fore or aft in frame??

Thanks before hand for any help. When i get a chance will post a pic, its at farm i'm at home. I know they're old, anywheres from late 40's to late 50's.