hi avery,
your model 12 was manufactured in 1919, value would be determined by barrel, condition ect. anywhere from 500 - 2500, check this site and see if any resemble yours.
http://www.gunsamerica.com/Search/Category/775/2/Guns/
Shotguns/Winchester-Shotguns-Modern/Pump-Action.htm
your model 14 was made from 1913 - 1934, a two or three letter date code on the left side of the barrel would indicate year of manufacture, value in good to excellent condition 450 - 550.
your model 12a made 190 - 1936 a model being the basic rifle, value should be 400 - 500 dependent on condition.
JMHO
Kim