The bird is the trademark of CAP, the type of steel used on this gun and is not connected to proof marks.
I don't have my reference book where I am but I would say early 20th century and certainly pre 1922 because the date code is absent.
Other giveaways are the barrel weights in 1/10 of grams and the "12 C" mark.
6873 is more than likely a subcontractor work order number, and is not involved in the proof mark either.
70 is indeed chamber length and 20.4 is chamber diameter.
Best regards,
WC-
Last edited by WildCattle; 01/10/15 03:28 PM.
