(1915 Pan-Pacific Exposition) Model Post Office, S.F. Cal., Gen. Del., Apr 28, 1915. Purple cds (Bomar SF15-06A) on Exposition post card addressed to the Expo P.O., franked with 2¢ Pan-Pacific, perf 10 (s.e. at bottom) tied by San Francisco machine postmark, Very Fine, the earliest known example of this very rare Model Post Office postmark. Scott No. 402  Estimate $200 - 300. Exactly 9 examples are currently known, one on post card dated 30 June 1915,and eight on the reverse of Commandant Exposition Guards registered covers returned to the Model Post Office in March 1916. $0 (Image)