I photographed these German 25cm Minenwerfer examples (long barrel and short barrel) at the Brussels Military Museum
Minenwerfer Schwerer 25cm a/A
When the 1912 design becomes outdated, the mortar name is appended as a/A (alter Art = “old model”)
Brussels Military Museum 2026
Minenwerfer Schwerer 25cm n/A
The 1916 update is labeled n/A (“newer model”) has longer barrel and better recoil system.