The left-hand flask is, indeed, a shot flask, adjustable by moving the upper cutoff between its 2 positions - which should be marked in ounces and fractions for the charge delivered. The right-hand flask is a powder flask, apparently for pretty large charges, likely shotgun, and should be marked in drams for each of the positions available by sliding the external sleeve.
The left one which is a leather shot flask and throws a charge on 1/1/4 oz and 1.1/2 oz of shot the right one is powder flask and will throw 2.1/2 drms up to 3.1/4 drams of powder mostly known has game shooting flasks, these powder nozzles come in all sizes the largest throws 15 drams for fowling for guns up to a 4 bore .They look like UK flasks of which most were made by Dixon and sons and Hawksley, I would date these flasks of around 1840 -1860
The sleeve is the external part of the spout, and is adjusted by pulling it away from the flask body and setting it at the slot for the appropriate charge. The sleeve is held in position by a screw engaging the slots in the sleeve - the sleeve appears to be present, but may be stuck.
Some flasks bear the maker's name, but not all. I agree with Feltwad on dating of the flasks.