wiring the locking ignition coil

Hi guys, just bought a locking ignition coil with key for my '29. This coil has the typical terminals on the end and also a brown wire which is about 8 inches long with a loop terminal that originates under the front (key) end. What is the purpose of this third wire and what does it go to? Also there are no positive or negative markings on the studs for dist. and ign., any ideas? Thanks

Shouldn't be hard to figure out with an ohm meter.

Here is what my 29 came with.

3 Studs Batt - Gas Gage - Timer I actually just completely ripped the whole thing apart and repaired it. Should be batt to power and timer to the distributor.

I have a rebuilt thread going on Chet's site. If you want to see all the parts in one its here http://www.1948plymouth.info/28Q29U/index.php?topic=811.30 toward the bottom of the page.

Here's what I had to figure out to get spark out of mine, copied it from the other forum because i don't want to retype.

"Got nothing no spark. I'm already scheming how I can attach a rotary switch to the back of the keyed and pot metal part of the ignition to make it function and appear stock. So I hadn't quite given up yet and head out to the garage with my fluke meter and start prodding. On my good coil I get about 1.5 ohms across - to +. Try it on the original batt to timer its open regardless of key position. Then I tried it from the gas gauge terminal to timer and get 1.5 ohms with the key on and open with it off. Wired it up temporary in the car, using the GAS GAGE terminal instead of BATT, coil wire to ground and open the points and zap! have strong spark!"