Edit: I think your diode sits face down ON the brass ring and that holds the diode in the groove on the back half.. It is REALY hard to tell from your pics, I'm just going on a hunch from experience.
sorry to tell you pol that is not it... I will just have to buy the real thing and hope i can find some one to buy these off me at what i paid for them 6.50
Those module are actually quite nice and I often prefer them because you don't need a diode press or extra heat-sinking if you don't use them for very long.
Here's how you put the diode into position:
Just feed the wires out the hole in the screw-on backing, put the diode into the bottom of the hole, and tighten. Other modules that don't have a separate brass fitting on the back just get held in place by the screw-on back.