Stop in for a cup of coffee

halifaxhops said

Pretty wild
Vtg Stewart Warner RPM Vibration Pin Tachometer TACH w/Case & Instructions | eBay

Click to expand...

That's a reed tachometer. I have one like this:

Frahm Vibration Reed Tachometer Resonant in box tach Type T-22 2000 to 4000 rpm | eBay