its a gun.Your Marlin model 778 shotgun is a slide action shotgun chambered in 12ga.Magnum.It was available in barrel length,s from 20in.to 38inches.It weights 7 3/4lbs. and was discontinued in the year 1984.Yours was made by Marlin sometime between 1969-1984.
Glenfield,which was made by Marlin Firearms Company made a bolt action .410ga shotgun from 1956-1965.This was the marlin model 59 which is the same shotgun as your Glenfield model 60.
Look up the Marlin shotgun with the same model number.
What do you want to know?
To determine exact value of a 1904 Marlin 12 gauge pump shotgun, you would actually have to take a number of factors into consideration. The main thing to consider would be the condition of the shotgun.
http://e-gunparts.com/ has themNo they do not.
Go to Cheaperthandirt.com
write to marlin with any and all writngs/markings on reciever/barrel and serial numbers
50-200 USD
100-300 USD
50-160
It has value as a shooter only - not a collector piece. $100-$200.
$1,000,000.00