Technical tachometer ID and wiring?

I got this tach at a swapmeet, does anyone know any info on what it might be and how to hook it up, does it need a sender? The markings on the back are as follows
12V 4CY
1549423
AC
MADE IN USA


Thanks

 

Mid 60s truck/tractor maybe. Looks a lot like an international tach I saw on eBay.

 

4CY might mean 4 cylinder?

how many of those threaded studs are insulated from the housing?

 

The middle, and the two under the mounting bracket are insulated

 

It's a marine tack listed for a Merc Cruiser
Listed here

 

since listed for a Merc Cruiser guess edisonfire needs to buy a Cool chopped Mercury Cruiser to put it in.

 

A guy I knew in Santa Clara had a '48 Merc flattie, complete dual ignition:
W&H dual coil, used a 4 cyl. electric tach wired to one side of the ignition.
Tach never knew the difference, calibrated properly...

 

That sounds like quite the plan!

 

well if anyone can use it feel free to PM me