Saw two (2) like this in inert spherical shells,10" if I remember correctly in Singapore in 1959 on my way to "British Jungle Warfare School".Think the tag said Naval. As a note this was the first school I ever went to,that the targets shot back.Before some one ask,For a run down of what was going on in Malaya,at the time, see the movie "7th Dawn" with William Holden & Sussie Wong.
Jack