You'll probably have to get some professional help on this one.
The Ithaca Hammerless was made in a wide variety of versions, grades, and action types.
It was produced from 1888 to 1948.
Price depends on the grade, style of receiver, type of checkering, grade of wood, type of triggers and ejectors, and MANY other factors.
Prices run from a low of $150 in poor condition for a standard gun, to as high as $50,000 for something like the rare John Phillip Sousa grade.
There are just too many versions and grades to be much more specific.
Your buddies gun looks to be a more standard grade, but in really nice condition.
Collectors are after good examples, so get some definite pricing from someone honest before selling it.
Doesn't look like it has Damascus barrels but the pic isn't real close & clear on the barrels.
I'd hazard a guess & say in the $600-800 range. But I agree with the suggestion an apprasial is in order.
Thanks guys. He looked online and said that Ithaca closed two months ago