BTW, 204's are considered non mule 1934's... correct? Are non mule 1934/non 204's more rare? Or 204's are the most rare?
1934 ("plain") $20 204 backs are in fact Mules. The 204 plate, while originally created in the "Micro" era (under 317), it was not completed and used for production until well into the "Macro" plate era. In fact, the "204" is a "Macro" sized back plate serial number paired with a "Micro" front plate. Thus it is a Mule.
However, since very few 1934 $20 Hawaii face plates were still in production at this time, most of the limited number of 204 backs were paired with series 1934A front plates. This is true across the entire $20 Federal Reserve notes of that time. 204 back plates are found on series 1934, 1934A, 1934B and 1934C. The 1934C notes are extremely rare as very few of these new plates had gone into production by the time the 204 back plates were retired and/or stocks of printed 204 backs depleted. The 1934Bs are the next scarcest, followed by the 1934, and, as stated, the 1934A being the most common pairing.
The Hawaii $20s were overprinted on San Francisco District face plates, with the 3rd printing being in brown ink instead of green. And a 4th and 5th printing (the black "HAWAII" on the front and back), were added.
The 1934 $20 Hawaii Non-Mules are quite scarce, and as mentioned above, no CU examples are known.
An Example of the 1934 204 lfp Mule.
A High Grade 1934 Non-Mule