binchicken
Unable to answer "What diameter is specified on the sign for this fire hydrant?" for https://osm.org/node/7772191085 via StreetComplete 38.2:

Diameter unclear, no sign

Attached photo(s):
https://westnordost.de/p/75024.jpg
https://westnordost.de/p/75025.jpg
https://westnordost.de/p/75026.jpg