Reader Fruity was the first to correctly name this device – on just the 9th comment. Impressive. Honestly, when I found this thing I had no clue. I asked other physicists and none of us were sure. However, I did find the answer. Let me show you my secret.
I don’t know how old this thing is, but it is old. When I open it, my nose and eyes get all tingly – probably from the mold. Here is that apparatus in the book (tome):
I can’t show you the whole page because it has other stuff of awesomeness that I want to show you later. But, I can show you the description for that item.
I am still giving Fruity the credit for the answer “Ampere’s Rule Apparatus”, but clearly The Tome of Knowing says “Mounted Conductor (Ampere’s Law Stand)”. Basically, you run some current through this thing and you can place a magnetic compass at different locations to see the deflections. Here, I made a quick video of it.