Can someone identify these markings?

[David Dunlop]

I have a piece of Artillery kit made by B.M.Co. of Canada, but there are no Canadian Military Markings or dates to be found anywhere on the item.

There is a brass plate on the top of the item with "MANUFACTURED TO D.N.O. DRAWING 7995" printed on it and stamped into the brass is a very small horizontal oval with A"Broad Arrow"M inside it.

I am curious as to what nationality the stamp may belong and for what the initials D.N.O. are the short form.

Regards

David