Funny thing our club had a horn seminar today, and I learned a few things from experienced hands. On all of the horns we discussed there were terminals connecting the field coil wires to the brushes. I didn't think to take pictures at the time
Also on the other end of the field coil wires the wires are or should be soldered to the clips. The wires usually yellow and blue, external from the horn with bullet ends slip under those clips. Something I didn't realize is that the gaskets sold today are too thin and need to be thicker. I doubled up on thin gaskets both sides of the diaphragm and my horn sounds better than ever. I had to scratch a lot of paint on my Ames to find the brand name and it isn't a very well stamp as far as depth, paint covered it with one coat. Look at your bracket, I found a stamp on it on the opposite side that it bolts to the horn.