This is very rare letter sent to camp prisoner when KL was - Zivil Gefangenenlager Stutthof ( civil prison camp ) 1941 !
First letters and any correspondence from and to KL Stutthof it very rare.
Second letters sent to camp its much more rare like send from camp.
Prisoners cant keep letter long time , just until next letter from home.
Third also in camp was big problem with paper for example : for cigarettes or toilet paper most prisoners fight for get paper !
Very rare item