Metal cylinder case with royal stamp

Anyone know what this is?  The handle slides along to close the box.
The person I got it from thought it was something to do with royal dispatches.
It's about 15"/38cm long and 3.5"/9cm diameter.

Map case?

Hah! I don't think she does that sort of thing outside the royal closet.

I'm confused by this case as the ER would imply it was made in the reign of Elizabeth, yet it looks older then the 1950s but not old enough to be Elizabeth I era. Could that ER mean anything else?

It may have been stamped later perhaps?

Also, Edward had an ER mark.

Ooh, Edwardian! That might make more sense style-wise. Thank you.
Still don't know what it is though. Maybe I'll send a pic to the queen, see if she knows. See if she wants it back to keep the family jewels in.

The present Queen's cypher is EiiR, standing for Elizabeth II Regina.

Perhaps badly stamped and missing the two little IIs

https://en.wikipedia.org/wiki/Royal_cypher

Looks like it contained some farm utensil. You only galvanise items that are going to be out left out in the wet, but need not to be disposable. So munitions would be cheepo tin / disposable and painted. Galvanising is an expensive process.

I took it to my local auction house and they said they thought it was something that would have had an official royal scroll in it.
Anyway, I sent pics to the museum at Buck House to see if anyone there could shed any light on it. I'll report back if they tell me anything useful.