WF500 head came in last night in matte black finish. The appearance was a perfect match for the 502c I intended to use it with. After unscrewing the bezel from the 502c, I just could not get the WF500 head to thread onto the 502C head properly.
I turned to my 502b, which has a glossy finish and the WF500 head screwed onto the WF502b head perfectly, which is really wierd, because so far, the 502b and 502c heads, bezels, bodies tailcaps have all been interchangeable. I tried using a dremel to sand down the threads just a tiny bit on the both parts and I can only manage about half a turn with the finish-matched parts.
There must be a microscopic difference in the TPI of the two 502 series lights I have, that's just small enough to allow the 502b work with the higher TPI 502c and the lower TPI 500, but doesn't allow the 502c to work directly with the 500.
If only the finish on all three lights matched! It's a shame too, because the extra length added by the 502 head makes the battery config I had planned actually work better for the color-mismatched 502b.
Stuff like this drives me crazy!