Registered mail is controlled by signatures of any postal employee handling the mail as it passes through the system. The initial stage is a certificate signed by the postal employee acknowledging receipt from the sender. These documents come in a multiple page booklet, the original staying at the Post Office and the carbon copy given to the sender.
As can be seen in the illustrations, the sizes and wording on the document changed with time. One constant, however, is the Post Office cancellation that makes it an official document. (Figures 1 & 2).
While this may seem a questionable item to collect, it is the first step in the movement of registered mail.