U.S. Small Panes
With the inflation of postage costs and the increasing use of self-adhesive stamps, the USPS converted from issuing sheets of 50 stamps to pane of 20. The new format made for a smaller pane, thus easier to collect. Also, there was room on panes to include Mast Heads and side-bars to highlight and detail the subject of the panes. Often setenant panes with 16 to 20 different stamps on a single pane, full panes became the only way to collect the panes.