Lot 209 Germany SC#C15 5m Vermilion 1923 Airmail Issue, With Expertizing Mark On Back, A Very Fine Used Example, Click on Listing to See ALL Pictures, 2022 Scott Classic Cat. $42.50 USD

A very fineused example of the 5m vermilion from the 1923 Airmail Issue, with expertizing mark on back. I don’t recognize this expertizing mark, and my attempt to look it up online was not successful. However, the cancel, while crisp, does have two elements which suggest it is genuine.
1) The ink does show a slight oily quality, bleeding into the paper ever so slightly. You can see this at the top of the 'S'.
2) The date line does have an "n" at the end, which is a characteristic of the genuine cancel. 2022 Scott Classic cat. $42.5.

Postally used stamps from the Weimar republic present a problem in that most are not of sufficient catalogue value for most to be worth sending off for a certificate. But they do tend to cartalogue much more than mint, and CTO, backdated or forged cancellations abound. However, there are generally two characteristics that you can look for, which will provide considerable comfort that a particular cancel is genuine, though they will not absolutely guarantee that the cancel is genuine: (1) look at both the colour and the appearance of the ink, specifically how it is absorbed by the paper of the stamp. The ink used during this period tends to have an oily greyish black colour, and it tends to bleed through the paper of the stamps. Very light, overly crisp or jet black cancels are almost certainly not contemporary. (2) Look at the line of the cancel containing the date. Typically all of the genuine CDS cancels that have the date displayed in a single line at the cancellation's centre will end with either a "V" or an "N". If they don't they aren't genuine in nearly all cases. In lotting stamps of this period we have carefully examined all the stamps in each lot and looked for both characteristics in each cancellation. We have noted, for each lot whether we believe the cancellations to be genuine and why. Some lots are backstamped with the expertising marks of the BPP to indicate that the cancels are genuine.