4-inch case with knurled rim

[doppz92]

Hello everyone, I have a few questions and I am sure someone will know the answers:

Believe it or not, my wife came back yesterday with a 4-inch case that she found in a junk shop. Not too sure she was buying the right thing, but because it looked good and had plenty of markings she went for it. We are on holiday in Britany and she paid 49 euros for it, which seems a very reasonable sumn. However, the case isn't in pristine condition because it was somehow recovered from the sea bed, quite likely by a trawler. This being said, it must have been quite a while ago because the markings are all very legible.
Could someone tell me who was the manufacturer? How common is this case?
Also, the entire rim is knurled, I read in another post that this was possibly for dummy/drill rounds, ok, but I doubt it, because this case was fired, and quite likely during the war which would explain why it ended up at the bottom of the sea. Could the knurling be to identify a certain type of shell in the dark, like illumination ones? Or am I completely wrong?

Thanks for your comments.

 

[Michel]

The milled rim I've seen indicated as sub-caliber and star shell but not certain. Nice find.

 

[Andy Naude]

I believe in this case it would indicate a star shell load.

A

 

[Andy Naude]

5.25 inch shell case

5.25 inch shell case with knurld rim

 

[radioman1]

Hi Had a quick look at the photo of the base

1 Looks like its a MK XV1 (16) but it hard to make it out

2 The case was manufactured by ICI in 1937

3 As far as I can remember the MK 16 was a fixed round

Hope this helps

Steve EX RNAD Trecwn

Ps What are the marking on the primer

 

[beihan62]

You married a treasure,hang on to her,
Cheers,
Don,

 

[doppz92]

Thanks, I didn't realize the picture was so bad...

Here are the markings:
12 O'Clock:
4 in Mks XVI & XVI* GUNS, then I below and the arrow
3 O'Clock:
ICI and what seems to be SB in an oval
6 O'Clock:
N and 1937 below and F to the left
9 O'Clock
BP in a rectangle, then 17.2(?).3
LOT 8 with LW in a rectangle below and a mark I can't read which looks like a messed up 47

Unfortunately the primer is too corroded and there's no legible marks.