From my understanding, the four digit shape number pipes are older (pre-1940) Two digit shape numbers were used from the 50's to the 70's. The stinger also helps date a Kaywoodie, someone cut the end off, so that makes it hard.
Here's a neat Kaywoodie reference page I saved:
http://www.otcpipes.com/files/Collector_s_Guide_to_Kaywoodie_Pipes.pdf