If I said M1907 it was in error. There are three versions of these fuzes, each intended for different caliber groups. The M1907 is a 21 second fuze, used on the smaller rounds - 75mm, 3-inch. The medium group then jumps to a slightly larger fuze, which jumps to a mid-30 second range (36?) This was used on 3.8-inch, 4.7-inch etc. For the larger rounds the fuze again increased in size and time. I have no pubs nearby and I'm away from the collection, but I believe that one was a 45 second fuze. This is what yours appears to be, look at the highest setting number. This was used on 6-inch, 155mm, etc. The larger rounds had further range/time in flight, needed a longer delay.
All of the numbers here are from memory and it has been a while since I've looked at any of the PTTFs to refresh my memory. If someone doesn't come forward with more accurate info remind me and I'll try and get into the collection one night after work.