If the SN is 401726 the gun was manufactured in 1928
Thanks to Walt Snyder, Ithaca Gun Co. factory letters are now available
https://centerofthewest.org/explore/...ecords/ithaca/
If the gun was ordered by a trap shooting 'top gun' it would add somewhat to the value. I'm with Stan regarding Knick values today. The stock extension and later White Line pad would detract from the market interest.
This might be of interest
https://www.trapshooters.com/threads...a-wins.894978/