12 gauge winchester 1900 made in 1899.In order to assist you in defining a value to your Winchester shotgun I will need to clarify some info provided and ask that you give a more detailed description of the shotgun in question.First I will say that Winchester made the model 1897 pump action shotgun,they made a model 1901 lever action shotgun in 10 gauge only.They also made the model 1911 semi-auto shotgun.So you must determine the model of your shotgun first.Then provide more info on the overall condition of the shotgun to include the amount of original finish remaining on the wood and metal,type of barrel(plain,vent rib,solid matte rib).All these things will help me assign a more accurate value to your shotgun.
120
Do a google search for "Winchester Model 12".
Winchester Model 12 shotguns in good condition can fetch prices from $500 up. 12 gauge is the most sought after size.
50-300 usd
50-450 usd
There is no 1600 series
50-300 usd
Around 1500.00
100-1000 USD
50-1000 USD or so
50-500 usd
A million dollars. ;)