Hey, this is NEAT!
Whoever did this one knew his stuff, unscrewed the base plug, removed the detonator, fuse and primer assembly with its ferrule and let the striker fly down through the open bottom of the bomb. The he reamed out the striker hole in the top of the thing and soldered in the screw-attachment for the actual lamp-housing assembly. We can't see the bottom, but likely he bevelled a channel into the base-plug for the wire, drilled out the rifle-rod socket and ran the wire up through there.
I do hope he boiled his Mills Bomb for a while before doing all of this. They were filled generally with 80/20 Amatol (TNT-AN mixture) and the stuff was cast in place. It melts out well below the boiling-point of water. TNT melts, I seem to recall, about 88 degrees Celsius, 180 Fahrenheit. If it has to be done, you use a double-boiler to prevent heat build-up in any one location.
I have a bunch of war-surplus furniture in my house, large stuff built by my Dad out of various and sundry airplane parts: lamp, table, couple of other things.
THIS thing is Trench Art at its finest in some ways, even if it is an awful mis-use of a perfectly good bomb.
NEAT!