Other people have thought the same thing. The DEC kit uses 1/4"-20 thread on its nuts and rods, which is the camera mount standard. It is also a UNC standard and a BSW standard.
I have measured the outer diameter of the thumb nuts to 3/4" in images. There is indeed a sharp step on the inside, and the diameter of the inside step is 1/2". (seen in an image from the Star Wars Chronicles where the blaster is photographed from the top/ahead).
As I have measured in images, and there is always some perspective in them as well as raster when they were printed and some skew when they were scanned, so I can not be more precise than that.