There is nothing more complicated than the history of the Imperial German Pioneer Units.This is marked to a Pioneer (Engineer) unit of the 19th Armee Korps.
The stamp is for the 1st Reserve Pioneer Company of the XIX Army Corps. But this unit existed only on paper. While its weapons, equipment, etc. were stored somewhere, the unit itself was never raised during WWI.
With the outbreak of World War I, each engineer battalion (of 4 companies) was divided into two battalions of 3 companies each. The second battalion received the 4th company and two new reserve companies.
It can be assumed that the planned 1st Reserve Pioneer Company of the XIX Army Corps actually became the 1st Reserve Company of Pioneer Battalion 22.