1911 Cartridge case markings

[Chetmandu]

My first post here - I've recently started more seriously collecting Great War artillery cartridge cases and trench art, primarily Canadian but also some British as well.
Acquired this 1911 naval case recently and there are a couple markings that I haven't been able to identify. The case is approximately 28.6 cm in length with a base diameter of 10.3 cm.
My question are about the stylised 'X' just above the '1911' as well as the two 'T' stamps. Any ideas on these?
Also, just about the Royal Laboratories 'RL' stamp there is a small "OK" stamp - is that as simple as it appears? An inspection approval stamp?
Rod

 

[ron3350]

I cannot help with the inspection stamps but the case looks like a cut-down 12 Pr 12 Cwt Mk1 case which often had the maker and dates in unusual positions. T is on lots of 3 and 6Pr cases too. 103mm is the rim diameter of a 12Pr, the base is measured above the rim.

 

[Chetmandu]

Thanks - I was wondering about it being a 12 Pr from what I've been reading and hearing.