15c Flag over Fort McHenry (15-star flag) Stamp (1978): How to Identify It

• Design subject and historical tie-in: depicts the flag over Fort McHenry, which Francis Scott Key watched being bombarded by the British from the Chesapeake Bay.
• Poem connection: witnessing the bombardment inspired the poem that became 'The Star Spangled Banner.'

The same design was issued in more than one form. Which one you have changes the catalog listing:

• Imperf error (Scott 1597e): Missing perforations entirely compared to the standard perf 11.2 issue.
• Booklet single (Scott 1598): A single stamp removed from a booklet pane, with a straight edge on one or more sides.
• Booklet pane of 8 (Scott 1598a): Sold bound into a pane of 8 stamps rather than as a full sheet.
• Coil (Scott 1618C): A coil-format version of the same 15-star flag design.
• Gray color omitted error (Scott 1618Cf): A printing error where the gray ink layer failed to print, leaving that color out of the design.

• Measure the perforations with a gauge; the same design often exists in two or three gauges, and that is usually what separates the common one from the scarce one.
• Sheet, coil or booklet: coils have two straight edges on opposite sides; booklet panes have one or two straight edges from the pane edge.
• Tagging: hold it under a longwave UV lamp; tagged and untagged printings of the same design are listed separately.
• Condition (centering, gum, cancel) is a separate question from identification.

Lay the stamp flat on a dark background in daylight, fill the frame, and keep the phone parallel so the perforations are not distorted. Photograph the back too if there is a watermark or gum question. The app reads the design and denomination; the perforation and tagging checks above settle which listing it is.