This is a training version of the Norwegian wooden mine M/1951C.
It was produced in large quantities in the early 1950s, and a large new stock was made in the 1960s. The plastic training version was made in the 1960s and 1970s, by the company "Bakelittfabrikken".
It continued to be the main anti-personnel mine (supplemented by the US bouncing mines M2 and M16) in the Norwegian army at least into the 1980s.
Info provided by Per Lilje.
Photos © M. Jochoms