The loss of the colonies in the early stage of World War I meant that the prices for cancelled stamps increased dramatically. This gave rise to a range of postmark forgeries. Illegal use of genuine cancellers, with backdated use also exist.
The cancellers consisted of a wooden-handled metal unit with interchangeable single digits for the dates and a single double-digit slug for the year.
The general rule issued by the German Reichpost was that stamps with Pfenning values had to be cancelled with one strike of the cancel, preferably centered. Mark values had to be cancelled by applying the cancel twice. Some collectors, however, preferred only a single cancellation centered on the stamp. These Mark values are ‘cancelled to order’, thus not genuinely postally used.