Model Ship

The Model Ship is one of of the 7 Larceny Targets which can be stolen from locations after you join the Thieves Guild. Once you have it you can sell it to Delvin Mallory for 300 Tibers (coins).

Location
It can be found in the Snow Veil Sanctum, in a room with a wooden stairwell & a stone stairwell. Take the wooden stairs & grab the ship.