This plate variety consists of a small line break along the edge of the bull's nose. It is uncommon in general, and since both stamps I find are NGR, it may be a late error.
This plate variety consists of a small in line within the inner lines of the 2 of 20 in the lower left numeral box. I have yet to determine if this is a variety that is found more than once on the plate. Here are three specimens. All are 2C.
Rein has recently discovered this stamp. At first I did not believe it, but here it is. It was 'under my nose' all along. The top row are 2D and the bottom row are 1E4.