I don't know if I mentioned it before, but I love compasses. This one is, aesthetically, one of my all-time favorites. This is the lensatic compass used by the United States military since the Korean War, and it is essentially unchanged from when it was first issued. The biggest noticeable change is that since September of 1992 it has been manufactured with Tritium markings, making it very readable in the dark.
As I said, aesthetically speaking, this is one of my all-time favorite compasses. It is, however, difficult to read and temperamental. When sighting, three different users will produce three different azimuth readings. Also, as a letterboxer, it is far more compass than you will ever need.
The main reason I include this compass in this little list is because they are available as used military surplus for very modest prices. Be wary, however, as there are many inferior replicas of this compass, so be certain that you are getting genuine military surplus.The current U.S. manufacturer is Cammenga, and they are stellar. I like old stuff, and will usually give old stuff the benefit of the doubt, but, in this case, you cannot do better than the current issue. Previously they were made by Stocker & Yale, Jay Bee Corp., Union Instrament Corp., Waltham Precision Instraments, Marine Compass Company and Lee and Stemwedel Inc. Though available inexpensively, the genuine article will rarely be cheaper than the Suunto baseplate model discussed below, and, for purposes of letterboxing, that is a much better choice. This one does look cool though. . . .