The object is a small steam ship, called "Drifter".
A naval drifter is a boat built along the lines of a commercial fishing drifter but fitted out for naval purposes. Drifters were robust boats built, like trawlers, to work in most weather conditions, but designed to deploy and retrieve drift nets. If requisitioned by navies, they were typically armed with an anti-submarine gun and depth charges and used to maintain and patrol anti-submarine nets.
The idea is to make a number of variants: One unarmed (fishing boat), one armed with surface gun and one armed with AAA. As soon as it's in a decent shape I will upload it so others can try the add-on in Rise of flight.
First results after one day:
Second update, added more details: