2 1/2 on 2 1/2 Groschen large shield in mixed franking with 1 Groschen large shield on forerunner of C.O.D covers official matter liable to payment of postage, cancelled by single circle postmark "DORTMUND ST. P. E. 2 27.9.74" and the rarely first violet adhesive label "Dortmund Stadtpostexp. II. / expenses" to Cologne with arrival postmark on the back from 28.9