It is always nice to find a not every day combination of postal services which leads to a single franking.
This envelope , 6.11.1942) from a notary has weights 49 gr, so second weight class. The rate for that was 10c (1.9.1937 – 1.11.1946). Registration fee was 10c (1.4.1939 – 1.11.1946). The contents are insured (red label ‘waarde’ (value)) for ƒ 713,92. The insurance rate was 2½ cent per ƒ 100,00 (16.2.1878 – 1.11.1946), so 8x 2½ cent is 20 cent. So all together 40c, paid with one stamp.