Carved letter meaning?

[Wolfssoldat]

Hello,
I have seen this blank label in all the field phones with carved letters. I am wondering why is that and the meaning of the letter? In my case it has a "K".
TIA.

[Witt]

According to the field communications writing, the writing tab on the left side of the lid was used to mark the station using the phone but could also be the receiving station. That does not give you much but it seems that this one belonged to a comms post that was known to the nachrichten truppe of whatever unit as ‘station k’.

This thread uses many of the diagrams from the original link further below:
FF33 - Variants and use

https://www.kriegsfunker.com/pdf/Ger...20of%20WW2.pdf

[Wolfssoldat]

That's more than I knew before so thanks for the input.