[1] The secret of Tarnsand was maintained until after the end of the war, when it was discovered that it was a mildly radioactive substance and the German mine detectors incorporated a simple Geiger counter.

The Topfmine B (To.Mi.B4531) was broadly similar to the "A" version, the principal difference being a smooth case without a raised pressure plate.

This version instead had an internal shear groove to prevent water from working its way into the mine and possibly deactivating it.

The Topfmine C (To.Mi.C4531 or Pappmine) changed the design to an eight-sided flattened cylinder shape, with a central glass fuze plug on the top.

This design was very thin-walled and sympathetic detonation could occur if the mines were planted closer together than seven feet (2 m).