Just something I picked up along the way to keep my brass engine oiler collection company on the shelf in the shop.
Most are 6 volt, I might have a 24 volt in there also. A couple of them show zero hours. The cloth covered wires are normally so weathered and unraveled that the meter shorts out and quits/fails.
Make sure you check out the wires before applying voltage if you come across one. There are 2 common mounts. Front row left is the smaller mount, and the one for the Cub is much larger and has a black rubber donut shock absorber between the meter and the mount ( not pictured here ). The large one in the back row has a bronze donut anti-vib harmonic stabilizer on it.
Update: If you need it, I have the install book from IH for Farmall Tractors and Crawlers. I also have the Case install book for S,D, 400 and LA series tractors.