The medal's obverse bears Americans from colonial to modern times walking, riding, and driving around the circumference, with some airplanes mixed in for good measure. In raised circular center, the American Bicentennial logo surrounded by AMERICAN REVOLUTION BICENTENNIAL / 1776 - 1976; signed with artist's (JOV monogram) at top right; at lower right, MACO / © 1975

The reverse bears square calendar panel in center, flanked by the PHiladelphia Christ Church steeple on the left and a launching Saturn V rocket on the right; Eagle holding streamer with THE / BICENTENNIAL / YEAR in its beak on top, Paul Revere on horseback at the bottom; at left bottom of calendar panel, 1976.

The American Bicentennial was a huge marketing extravaganza that caused a multitude of medals to be issued.   Marcel Jovine created a thematically appropripate design in his inimitable circular style. 

This is one of the few Calendar medals that were issued in different sizes.  A limited edition 3.75" medallion was offered to collectors in addtion to the normal 3" medal.  I am not aware of any medals in silver though I would not be terribly surprised to find out that a few had been struck.  The 1970s were a time of sky-high silver prices and 3" silver medals would have represented a significant investment.

References:   MACo 1975-134, Cal MA-1976