Wow, this is an odd one. I can only find a few photos of these things, and only one is of this exact style and it is a line drawing in a book.
This looks to be a very early first style example. In a 1909 book it is called "the Ideal Dynamo". Made by WM Gaertner & Co Chicago Later styles, apparently are called a" dynamo analysis apparatus" It appears it was used for teaching dynamo theory. It looks to be complete and have all of the parts. Most all of the black and silver parts are Brass, the magnets are iron.
If you actually wanted to use it, my guess is it would need a new spring and some restoration. The ideal dynamo shown [below] is arranged so that at every revolution of the crank the ratchet is lifted, allowing a spring to rotate the coil through 10°. The terminals of the coil are connected to separately insulated copper rings attached to the shaft. Copper strips or "brushes" bearing upon this ring are connected to a moving-coil galvanometer.As the coil moves through any ten-degree interval, an E. Is induced which corresponds to the mean angular displacement of the coil from its original position. Since the total resistance through which this E. Causes a current to flow remains the same through the experiment, the quantity of electricity passing through the galvanometer, and therefore the galvanometer deflection, is proportional to this E. If the observed deflections are plotted as ordinates and the corresponding values of the angular displacements as abscissas, the smooth curve drawn through these points will in general have practically a sine form. From Robert Andrews Millikan and John Mills, A Short University Course in Electricity, Sound and Light (Finn and Company, Boston, 1908) pg 134 (SEE LAST PHOTO). About 11 inches long, 8lbs, horseshoe magnets still appear to have some power. No one can be expected to be an expert at everything. I have done my best to describe the item accurately, and in an honest opinion. It is highly suggested you look at the pictures, and read the descriptions to determine if the item is what you want. What you see in the photos is what you get! WHAT YOU SEE IN THE PICTURES IS WHAT YOU GET! IF YOU HAVE QUESTIONS ASK! The item "Rare Antique 1800's Dynamo Teaching Model used with Galvanometer Bipolar Motor" is in sale since Sunday, February 17, 2019. This item is in the category "Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Other Antique Science Equip".
The seller is "ranger_rick" and is located in Algonquin, Illinois. This item can be shipped to United States, Canada, United Kingdom, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Australia, Greece, Portugal, Cyprus, Slovenia, Japan, China, Sweden, South Korea, Indonesia, Taiwan, South africa, Thailand, Belgium, France, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Germany, Austria, Bahamas, Israel, Mexico, New Zealand, Singapore, Switzerland, Norway, Saudi arabia, Ukraine, United arab emirates, Qatar, Kuwait, Bahrain, Croatia, Malaysia, Brazil, Chile, Colombia, Costa rica, Panama, Trinidad and tobago, Guatemala, Honduras, Jamaica, Viet nam, Uruguay.