Recommended stamps to settle printing issues

The best stamps to study by era to settle most printing method issues, in my opinion, are:

1. The 10c Rivadavia Red settles issues for the 1935-1936 period.
2. The 15c Small Format Cattle, both colors, is good for the 1935-1939 period.
3. The 25c 1Es settle usage issues for the 1939-1944 era.
4. All of the unwatermarked grids (NGR) are from 1945/46/47.
5. The bright white straight rays large format stamps (2C) paper, are good to settle usage for 1949/50.
6. The 20c Small Format Cattle was only used between 1951 and the mid 1950s.
7. The 50c 1Ls are good for the 1951-1956 time period.

Notice that I have omitted the ridiculously common 10c Rivadavia Brown. I have a simple reason: there are too many printings to separate for this stamp before using it to figure out a printing method issue.