Are the inspectors' marks above the provisional BP proof marks star over L; If so should be Antoine Salmon 1937...1968.
Leon Chesnoy 1927...1955 & 1959...1968 for the star over Y on action flats.
According to "Gun Proof in Belgium" by Lee Kennett in the "1978 Gun Digest" under the system of 1924 the ordinary provisional proof for 20 gauge barrels complete save chambering at 11,700 psi was 11 grams of powder and 42 grams of shot and the definitive black powder proof at 9,100 psi for maximum chamber length of 2 3/4", 9 grams of powder and 33.3 grams of shot.
According to Kennett the two separate nitro proofs were "theoretically optional" under the 1924 rules of proof.
Markus
