25 Pfennig, Burg an der Wupper, 1921

Notgeld began in 1914 as necessity: silver and nickel coin vanished into hoards within weeks of mobilisation, and towns printed their own small change because the Reichsbank could not supply enough.

By 1920 it had become something else entirely. The shortage was easing, but the market for the notes was not - collectors would pay well above face value for a complete set, and a town could take real marks for paper it hoped would never come back to be redeemed. So the municipalities commissioned Serienscheine: lithographed series, four or six or ten notes to a set, printed far beyond any local need and illustrated with whatever the place was proud of. Local legends, famous sons, battles, saints, jokes in dialect.

The result is the most inventive body of graphic design in the history of paper money, made by places with a few thousand inhabitants, in the years when Germany's currency was dying.

Burg an der Wupper is a small town in the Bergisches Land, east of Düsseldorf, and above it stands Schloss Burg - the ancestral seat of the counts and dukes of Berg, abandoned in the sixteenth century, ruined, and then rebuilt from 1890 onwards as a monument to the region's own history.

The set is unlike anything else here. The face is a single pen drawing of the castle on its wooded hill, identical on all five notes, with the denomination, the date of 1 December 1921 and the mayor's signature below. The reverses are photographs - halftone plates of the rebuilt Rittersaal, of history paintings hanging inside it, of the murder of Archbishop Engelbert. No woodcut, no dialect, no joke. A museum illustrating itself on its own currency.

This is the 25 Pfennig. Its reverse is captioned Ansicht des Rittersaales and shows the interior of the rebuilt knights' hall, a long vaulted room with a timber ceiling.