To me the maker's mark appears to be HP with sword in a rectangle shaped frame for H. van der Plaats, registered in Joure, 1920-1961, the sword mark with 835 used 1953-present.
H. van der Plaat could be Hendrik van der Plaat, born in Joure 23-07-1895, died in Joure 24-11-1975.
Peter.