The complete set in detail
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ESC16
SG No. O C16
1964 - Official stamp : Inscription 'DDR ZKD' and '1150', Bln (Berlin) - orange / magenta
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ESC17
SG No. O C17
1964 - Official stamp : Inscription 'DDR ZKD' and '1060', Cbs (Cottbus) - olive / magenta
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ESC18
SG No. O C18
1964 - Official stamp : Inscription 'DDR ZKD' and '1120', Ddn (Dresden) - violet / magenta
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ESC19
SG No. O C19
1964 - Official stamp : Inscription 'DDR ZKD' and '1090', Eft (Erfurt) - emerald / magenta
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ESC20
SG No. O C20
1964 - Official stamp : Inscription 'DDR ZKD' and '1050', Ffo (Frankfurt/Oder) - blue / magenta
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ESC21
SG No. O C21
1964 - Official stamp : Inscription 'DDR ZKD' and '1101', Gra (Gera) - ultramarine / dark ultramarine
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ESC22A
SG No. O C22
1964 - Official stamp : Inscription 'DDR ZKD' and '1081', Hle (Halle) - brown / dark ultramarine
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ESC22B
1964 - Official stamp : Inscription 'DDR ZKD' and '1082', Hle (Halle) - brown / dark ultramarine
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ESC22C
1964 - Official stamp : Inscription 'DDR ZKD' and '1083', Hle (Halle) - brown / dark ultramarine
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ESC23
SG No. O C23
1964 - Official stamp : Inscription 'DDR ZKD' and '1141', KMS (Chemnitz = Karl-Marx-Stadt) - dark lilac / magenta
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ESC24
SG No. O C24
1964 - Official stamp : Inscription 'DDR ZKD' and '1131', Lpz (Leipzig) - red / dark ultramarine
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ESC25
SG No. O C25
1964 - Official stamp : Inscription 'DDR ZKD' and '1071', Mbg (Magdeburg) - carmine-lilac / dark ultramarine
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ESC26
SG No. O C26
1964 - Official stamp : Inscription 'DDR ZKD' and '1030', Nbg (Neubrandenburg) - green / dark ultramarine
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ESC27
SG No. O C27
1964 - Official stamp : Inscription 'DDR ZKD' and '1040', Pdm (Potsdam) - olive / dark ultramarine
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ESC28
SG No. O C28
1964 - Official stamp : Inscription 'DDR ZKD' and '1011', Rst (Rostock) - violet / dark ultramarine
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ESC29
SG No. O C29
1964 - Official stamp : Inscription 'DDR ZKD' and '1111', Shl (Suhl) - orange / dark ultramarine
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ESC30
SG No. O C30
1964 - Official stamp : Inscription 'DDR ZKD' and '1020', Swn (Schwerin) - orange-yellow / lilac-red