Anyone ever seen, used one of these before? How does it work?
It is what is commonly called a "buzz box" type coil tester. You hook up a (typically 6V) battery to the 2 thumb screw wire terminals and then insert your T coil with the bottom of it towards the meter. If it is working you will see a DC current measurement on the meter and a spark at the adjustable thumb screw that will be arcing to the spark plug wire terminal on the side of the coil. They make noise and I suppose tell you that the coil is not totally dead but as a real tester they have limited use and there are countless versions of this type of coil tester that all work on the same principle. They are collector's items more than anything else. In the T era these were just another garage type business operation trying to get in on the $$$ to be made on T parts and test equipment.
Thanks John for the explanation. It may be totally useless, but somebody used some nice Teak in its construction.
50+ yrs ago I made a tester see if I can put into words - drop a coil in, a coil wire goes to a
grounded spark plug. I have a grounded wire on a
pivit - a stud sticking up that also goes to the
coil plug wire. Plug in 6vts and the coil is
buzzing and the spark plug is sparking, now rotate the wire that opens gap to the stud now that is sparking
like the plug rotate wire away from stud and see
how long the spark jumps then I tune the points
till I get a long spark and get a smooth buzz.
Both have a nice blue spark. I have a 1940s or 50s Blue Point tester same deal but for regular
coils. this has a ecentric (like my wire & stud) with coil plugged in you rotate the ecentric disk it is marked bad good excellent,
rotate until the spark stops & when it does read what it says like jumping spark 1/2 or better is exellent the bad is spark peters out
as soon as you move or open the gap. best I can
Although there are those that disagree with such a devise - being accurate and such - it is useful and can help with coil testing and adjustment. Here is my home brew version. As a side note the Dykes Motor manuals describe these in multiple editions.
I bought a couple coils off eBay that came with a coil tester. I guess this would tell you if a coil works or not, but that's about it. I guess it could have been part of an HCCT or used for an electric fence somehow, but by itself it's not much good.