6Pdr Blackened base

[Dandebur]

Hello,
Found this week two cases of 6 Pdr, not naval, headstamp K 1917 lot 77 and 88, with a blackened base. I think it is not incidental, perhaps I had yet seen that, but I never took care to this fact.
Can someone explain the reason?
Thanks in advance,
Dandebur.

 

[ron3350]

The cases for the early tank guns were blackened for half the case length. I have not seen just the base and bit blackened before.
The red markings are definitely over the black base so maybe the same meaning - lower pressure for tank gun?

 

[ron3350]

This is my example.

 

[Dandebur]

ron3350,
Thank you very much for your reply. So for use in tank gun. This case is not common but also not very rare in my country but I have never seen one half blackened as your.
Regards,
Dandebur.