Question about Dixson single cylinder wireless tach

[roveron]

I picked up one of these at a thrift store last night for $3.

I was going to just stick a battery in it and test it, but don't have a 9v battery on hand.
So I thought I'd go ahead and ask:
Does the coiled spring "antenna" that extends from the back actually connect to anything inside?

I opened it up to see what battery it takes and the retaining nut on the inside isn't connected to anything.
I couldn't find a manual online anywhere.

 

[president]

that is the same tach that baileys sells under the oregon name
some dont like the analogue because of the osscilations ,but it works
great for me .they list out at $ 120 or so and you can purchase the antenna
lead for $ 10 and it screws onto the outside top screw, and the battery is replaceable!