YieldMapper
Unable to answer "What diameter is specified on the sign for this fire hydrant?" for https://osm.org/node/3846198999 via StreetComplete 38.2:

Da steht nur "b 75 DIN 14318" und am Halter pvr 1/84

Attached photo(s):
https://westnordost.de/p/75414.jpg
https://westnordost.de/p/75415.jpg
https://westnordost.de/p/75416.jpg
https://westnordost.de/p/75417.jpg