I have a specialized collection of Frankfurt am Main as a City State. Frankfurt did not issue its own stamps,and its mail was handled by Thurn and Taxis. So before T and T issued its own stamps, all Frankfurt postage is noted by cancellation and transit stamps. The postal clerks noted amount paid and other information by pen marks on the front of the cover. These evolved over time. My earliest example is from 1793. The cancellation is a straight-line stamp. A circular date stamp was introduced in the early 19th Century. There are several designs. When T and T stamps and pre-stamped stationary was introduced Frankfort mail was cancelled with a 'target' cancel and the number 220.
The example below is T and T stationary, mailed in 1866. It has the 200 cancel. It is intra-city mail. It has a rubber stamped notation, and it is this that is puzzling me. Do any of you know what the notation means? It reads: