Arnold Mfg Co dwell tester

[bctexas]

I like old engine test equipment, and when I came across this curious gizmo on Ebay I had to have it. It is an "Electronic Cam-Dwell Indicator". The sum total of the "electronics" consists of a AA battery and a flashlight bulb. So the idea is, in the car you mark where the rotor is in relation to the distributor, then mark where the distributor is in relation to the block. Then you loosen the distributor hold down clamp. The "Indicator" has a magnet to stick it to the side of the distributor (and a hooked metal slip to hang on an aluminum distributor to stick the gizmo to if needed). You connect the alligator clip to the points. Then you turn the distributor housing till the light comes on (points closed as in the picture) and aim the pointer at zero. Then turn the distributor housing until the light goes out, and read the dwell on the scale! Then realign the marks you made earlier and tighten the distributor back down. It works!

It comes in a nice fitted flip up case, with instructions and a list of dwell specifications for American cars up to 1959. That is the only mention of a date I can find on it. Can't say I have ever seen one before!