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
built in 1908, 104 yrs old
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.
If that is an old double barrel "New Ithaca Double" it was made in 1926.
I have a 12 gauge shotgun with the numbers 4041 on it. It has a double barrel and double trigger and hammerless. Could someone tell me what year it was made?