It's former German Torpedoboat A 64. German A 56 (Vulcan) class. Build by Stettiner Machinenbau "Vulcan", Stettin (Szczecin). Launched 30.03.1918, delivered 08.08.1918.
From 1921 as Krakowiak in Polish Navy. Decommissioned and scrapped in Poland in 1938.

I've changed my comment.
KRAKOWIAK seems indeed being her name. During some searches I found that the Polish torpedo boats had their names as initial letters on their bows.

Unluckily I found no pics or specs on her even when googling for "torpedowiec orp krakowiak"

Regards,
Werner

KR on her bow - that means: Krakowiak.
Torpedo boat