The John Deere Models B, A, and G were three machines tractors in the series of consecutive models in the letter series. The B was the smallest, followed by the A, then the mighty G, which was the largest of the row crops. To make this a complete series of row crop lettered series tractors, I would simply be missing the Model M, which would be the smallest of the group of row-crop models. There was also the models D and R, which were “standards”, and not row-crop.