Your serial number indicates that you have a Ithaca crass model double,that was made in 1903.
It is only worth what the person buys it for...
http://www.gunshop.com/dgsnos3.htm
Numrich Gun Parts Corp. online at ww.gunpartscorp.com
this is a Lewis model made between 1905 1910.
It sounds to me like you have a Early made Ithaca Baker model double barrel shotgun made in 1889-1890.As to value I would have someone with the knowledge to evaluate you gun and then he could assign a value for you.
There's a list of serial numbers by year at http://ithacagunrepair.com/page5/page23/
I am not sure about the age or value, but I would sure like to own it to rabbit hunt with.
Ithaca SN 68814 was manufactured in 1902 according to Ithaca Gun Company records compiled and released in 1960. It is a Lewis model if hammerless and New Ithaca Gun if it has hammers.
Go to diamondgunsmithing on the internet and enter your serial number. That will do it.
If that is an old double barrel "New Ithaca Double" it was made in 1926.
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.