ancient gauge. terminals aren't labeled. can someone identify them for me?

[Mrcleaningguys]

My tach froze. I found an old one in the garage but don't know the terminals. Can someone identify them for me?

 

[alldodge]

My tach froze. I found an old one in the garage but don't know the terminals. Can someone identify them for me?

My guess would be something like this, only issue is that pos and neg might be swapped then what is shown in this pic