A separate post on SCF today was referring to some of the military FDC and cachetmakers of the 1940's.
For those interested in the US Merchant Marine Stamp (Scott #939), the following web site has done quite a nice job of identifying many of the cachets used on First Day Covers for that issue.
http://www.usmm.org/fdc.htmlJust thought I'd post the link for anyone interested in such a study.