The photo's fine. The stop pin is the copper/brass colored peg coming out the top of the condenser mount just to the right of the steel mounting block and above the condenser focusing knob (as shown in the photo). The allen set screw is in the side of the condenser mount and appears to be at the front and below the peg. If you loosen the allen screw be sure that the peg cannot pop out.
g2b2