Im not very familiar with them and found a gun of interest, its about a 1928-1935 vintage,its 12 bore,(12 C in a diamond) thu it does not have the actual barrel dimensions marked as I have seen on some. nitro proof I can tell,and doesnt seem to have choke indicated just stamped"choke"
has a crown over each of these letters "Bp" "BV" "NP" any info is greatly appreciated Don