At first glance this looks like two ordinary pairs of Joker hardcopy arms. The picture shows a pair of arms that match the stance on the produced figure as well as a pair which includes an alternate version right arm.
Here we see a nice close up shot comparing the two versions of the right arm. The top arm represents the version used for the released production toy. The bottom arm exhibits a few noteworthy differences. First, it features a slightly different sleeve end which is more angled. Second, the hand exhibits a more curved stance. Lastly, the elbow sculpted differently giving it a more pronounced look. These differences show a sculptor's meticulous attention to detail in order to arrive at the most appealing final version of a figure.
Hardcopies are produced using a silicone mold (this mold is created from the original wax figure sculpting). Once it is removed from the mold it may serve a number of purposes. It might remain unpainted and ultimately be used to create a negative epoxy "hardmold", which is used in the cutting of the steel production mold. This negative epoxy mold is essential since one cannot pantograph from a positive object to yield a negative mold. The process must be done from negative to negative. When used for this purpose, the hardcopy is referred to as a "tooling master" or "tooling hardcopy".