Since I'm posting here now, Transitional 'M23' Adrian - probably used by the Spanish during their civil war (elaboration in captions) : r/Militariacollecting
Denmark M23 World War II helmet, complete | #150529012
Military Antiques and Museum - - DWH-0001 Danish M23/39 Civil Defense Helmet - $49.95
Lot 590 - Group of various military helmets to include
Philip's Military Helmets - Highly interesting photo of the British rolling into Denmark, 1945, with Danish resistance members in the foreground. If one looks closely at the helmets that the Danish resistance
Netherland M23/27 - Brendon's Helmets
3) DANISH ARMY M23 Steel Helmet £49.99 - PicClick UK