Probably refers to K .Kloosterhuis who lived between 1930 and 2004. Post-war (even after 1945 Sikorskiego street had B. Pieracki as its patron) printed business card: Finished and custom furniture Kloosterhuis Klaus master carpenter. Swarzedz, k .-Poznan, 16 Sikorskiego St. tel. 175 ext.75.
Sheet measuring 6.8 x 12.5 cm. Good condition, soiling vertical discoloration(?), stains.