I'm pretty sure the fob depicts a scene associated with the incident between the U.S. and Mexico in the early part of the century.
Additional info can be found here...
http://militaryhistory.about.com/od/battleswars1900s/p/veracruz.htm
Lacking the authority to grant Mayo's demands, Zaragoza forwarded them to Huerta. While he was willing to issue the apology, he refused to raise and salute the American :usaflag: as Wilson had not recognized his government. Declaring that the salute will be fired, Wilson gave Huerta until 6:00 PM on April 19 to comply and began moving additional naval units to the Mexican coast. With the passage of the deadline, Wilson addressed Congress on April 20 and detailed a series of incidents that demonstrated the Mexican government's contempt for the United States.
A nice relic. :clapping: thanks Joe