I believe the Waterloo Boy tractor fob was a John Deere product.
From my very limited online research, it appears that in 1895 the Waterloo Gasoline Engine Traction Engine Company was sold to John W. Miller, and renamed the Waterloo Gasoline Engine Company.
In 1918 the company was purchased by John Deere. So I am thinking this fob must have been produced somewhere in that range. The fob itself is metal. Brass maybe?
There appears to be some enamel filling in the large WB letters on the front. The front features a large W and B. A ribbon above with the words Waterloo Boy, and a ribbon underneath that says Gasoline Engine. A gasoline engine is in the center.
Above the top ribbon are stamped the letters J V. I am only guessing that this may have been stamped with a die by the owner of the fob, and is not original to the item. It does not distract from the fob though.The back has the following text: Waterloo Gasoline Engine Co. Makers of buttercup cream separators, one man tractors, one ton motor trucks. Sold only through dealers.