I'm told this is a poor mans model t coil tester. It would hookup from the coil to the spark plug wire. You would ground one of the screws and adjust the gap between the pointed screws while playing with coil adjustments and look for the best spark.
It might help some, but the real important thing is to get your spark at 1.3 to 1.5 amps on each coil. If one coil takes more amps to spark than another your timing will be slightly off between the cylinders and cause it to run rough. You need a "rich mans" coil tester or strobospark. If it is too expensive for you, you could pool with other club members in your area and together buy a good coil tester.
Norm
Norm, You are absolutely correct that coils should be setup on a HCCT. I was just showing a gizmo someone used 80 years ago. I do indeed have an Allen Electric Co. HCCT Norm
Norman,
I'm thinking that what you have there is a homemade lightening arrester for an outside radio antenna.
Norman,
I've got one of those in my tool box, it's used to test the "spark" from your ignition system. On a lawn mower, if the spark will jump across the two pointy ends,(in open air) it will fire the spark plug under compression.
Here's a picture of a newer version.