Unless special ordered otherwise, a 16-gauge Parker Bros. of that vintage would have started life with chambers 2 7/16-inch deep intended for the 2 9/16-inch 16-gauge shells of the day.
SUPER-X 16-gauge, 2 9-16-inch, FIELD, #5 Chilled Shot 02.jpg
What the chambers are now can only be determined with proper measurement.
All the metal on the gun has been improperly refinished. When I see a frame blued like that, that should be color case hardened, I worry that someone who did that may have also hot blued the barrels, the salts of which will now be attacking the solder which holds the barrels together.