Picture is out of focus because my camera thought I was taking a picture of the box flattened on the coffee table instead of, you know, the big black piece of plastic.
Top has +/- for electrical connections; says “Use with External Resistor”, pretty heavy, about 6 inches tall.
Probably something really obvious to someone who isn’t me.
Once you said “Top has +/- for electrical connections; says “Use with External Resistor”, pretty heavy, about 6 inches tall.” I knew what it was. I did not look at the picture.
Pretty much, you will need to take it to a parts store, or a repair garage to find someone with the machine to test it. I would just replace the one in my truck with yours & try to start it, if the truck runs & drives OK for 30 minutes, it is good. Around here, they go for about $10.00 used.