I'm no expert, never owned one of these but I have seen a few around. Please correct me if I am wrong.
175 The original straight frame design, with behind the cab boom arms that came down alongside the operator, if he stuck his arm out they could hurt you.
175a A more modern looking straight frame machine with boom arms that are hinged ahead of the cab.
175b An articulated frame design, early rops had long back braces going down to the frame near the rear.
175c Modern design, got the rops inside the cab, cab still has a square, box like structure, vertical windshield.
In my opinion, the op's picture looks like a 175b to me.