SPECIAL POLICE UNITS - UPPER SILESIAN SPECIAL POLICE, 50 Pfg dark grey, 3 Mark violet Steelworks and Dove of Peace 1920 on cash-on-delivery letter (amount 9,35 Mark) to Halle a. d. Saale, double-circle KATTOWITZ 22 4 20 * (OBERSCHL) (OS handbook no. 141.18), violet single-circle unit mark Spezial-Polizei Oberschlesien Gruppe Kattowitz (Katowice) Brief-Stempel (OS handbook 3.5.b.), arrival (29.4.1922), age and use wear typical of period