An Armchair Analysis:
The prop has a top and a bottom. The top is the taller half with the antenna; the bottom half is shorter, with a large screw. It also has a front and a back. Those are less easy to differentiate, but the antenna & the big bottom screw seem to be on the left side, when viewed from the front. That also makes the smooth side (& screws) the right side of the front, and puts the ridges on the left side of the front. If so, then the back side of the device is 'mirrored,' with the smooth side on the left & ridges on the right.
Additionally, the back side appears to have 5 silver-tone screws (?), presumably to secure the innards & the sliding mechanics. We have a couple good pics of the front, from the auction, but no pics of the back, save screencaps.
However, the Cap's broken transponder has the antenna on the left and the smooth side on the left, which suggests it was assembled incorrectly, or something.
-MJ