I've seen lots of different RZM M7 / xxx maker codes over the years. I had no idea how many there actually were. A little research tells me there were 129 makers total! Does anyone know why there were so many? Maybe this was an effort to improve the economy and give people jobs as well as increase sentiment towards the war effort in Germany. From what I found, there were 82 original makers under the RZM code as of 1938 (published by the nazi political party in 1938), and then later in 1938-1939 they added more, but some (numbers 10, 26, 39, 69, 75, 81, 82, 87, 90, 96, 100, 105, 106, 113, and 116) were 'withdrawn' from production permissions. Once Austria was annexed by Germany, about 10 more were added to get the total list we have today (this also explains why the numbers are in sequence and then jump at the end. Perhaps the nazis were planning on having MANY more maker codes).
Not sure what production numbers were like from each, but I'm sure some are more scarce than others