Mobile Post Office Society (MPOS) was founded in 1950 by a group of philatelists interested in the study of United States Highway Post Offices. It soon expanded to focus on Railway Post Offices, and eventually to the enroute distribution and postmarking o
Annual dues for membership in MPOS are $23/year for "ordinary" membership which includes a subscription to "Transit Postmark Collector," the journal of MPOS which is currently in its 47th year of publication. "Sustaining" membership is available for $38/year, which includes an additional publication per year at no extra charge. "Patron" membership is $53/year which includes two publications and an extra discount on literature. "Family" membership is available for an additional $5/year. A dues discount of $3 is offered annually to early payers. Part of the dues for "Sustaining" and "Patron" membership can be considered to be a tax-deductible contribution to MPOS, and all outright contributions to MPOS are tax-deductible.
