This is a 1923 Free City of Danzig (Freie Stadt Danzig) airmail (Flugpost) stamp, overprinted with 5 Millionen (5 million marks) during the hyperinflation period.

1. Original Stamp Details:

• Type: Airmail (Flugpost) stamp

• Original Value: Likely 20 Marks (before overprint)

• Design: Features an airplane with sunburst rays and “Freie Stadt Danzig” lettering

• Color: Orange-red

2. Overprint Details:

• Overprint Value: 5 Millionen (5 million marks)

• Overprint Type: Thick, black Gothic font typical of 1923 hyperinflation issues

• Issued as a part of a series to cover skyrocketing postal rates for airmail services.

3. Collectible Value Insight:

• This series is popular with collectors, especially when overprints are clear and well-centered.