Hello, This German registered letter,???

If the letter remained, within Germany, the part with the barcode was usually removed upon delivery. It was stuck on the receipt that the addressee had to sign, and that remained with the letter carrier. Abroad, they only noted the number and transmitted it back to Deutsche Post, thus the label remained complete.

Those are two registered letters from the 90ties. The first one stayed in Germany, the second one was going from Germany to Switzerland. Both have a serialnumber!

How was a registered letter handled inside Germany? At the postoffice you got a receipt/bill which was printed with the serialnumber. For the letter was printed a label/sticker with a second label/sticker on it with the barcode (like on the letter to the switzerland).

When now the post man in Germany was coming to the receipient, he removed the second label/sticker (with the barcode) put it on a receipt and the receipient was signing it.

In Switzerland they may be have still copied the serialnumber manually to the receipt.

Where ist the serialnumber, you find it always right of the red R

At the first letter it is in the first row of the label/sticker. At the second letter it is in the first row and below the barcode.