Help with old 1915 Brass shell.

When I was a Kid I collected Brass shells. There was a shell in my Great Grandmothers farm house that was used as an umbrella stand and sat in
the corner for years. When I asked about it as a child I was told that
it was presented to my Gran Aunt or great gran aunt around 1915 as a present by an Army Cadet.

Around the early 90's some of the relations passed away and I basically ended
up with getting a present of the shell. In the 90's it was valued at having a price range of 4-600 Irish pounds.

I went googling before but never turned up much information about it.
I was guessing it may have been from a Ship? or some google results
showed German howitzers I would like to know more info about it as in
what fired it and what it looked like before it was fired I would love to make
a dummy head for it to see it in all its glory.

Have some pics below. Anyone got any info on it?
Its about 155mm wide at the neck and a little over 3 feet high.
Has the words Polte and magdeburg on it as well as a makers stamp?

I have seen this site before but it does not give much info
http://home.hetnet.nl/~supersmit/ww1/stamps2.html

Theres a 50cal drill round and a 40mm AA shell in the first pic for scale.