I found this at the Nats.
Slotts
Hey, I just bought one of these about a month ago. Wanted to post it here but I have been having camera issues.
Mine is a C-4166A. According to my manual it came out after yours and the differences seem to be that yours needs an adaptor for some test(s). Mine has a light where yours has C-4166 and there seem to be more instructions on the back.
I bought it quick and didn't have much time to research it. Couldn't find much info and really have no idea what they sell for. I paid $40 for mine and thought it was worth it just for the 'cool' factor in the shop. I have no idea if that price is good, bad or right on. What did you pay for yours?