It sounds to me that you have a Ithaca Flues model double barrel shotgun.With the serial number that you provided,your shotgun was made by Ithaca in 1917.
The age of an Ithaca can easily be determined from the serial number. What is it?
11169
1000.00
The serial number indicates your gun was manufactured in 1949.
1950
1947
1949
1938-39
The Ithaca side by side 12 gauge serial 188650 was made in 1927.
Go to diamondgunsmithing on the internet and enter your serial number. That will do it.
The gauge is stamped on the water table by the serial number. It is a Flues model made in 1924.