Need Help Id'ing this Shell says MK2-17 A 11-42 around top

[scottl]

I have this shell that i Can not id. i believe it is from WW2 as It came from grandfather and he was in WW2. it is heavy and a little bit over 17 inches long.
Around top are the #s MK2 17 A 11 42 bottom has numbers and what looks to be an anchor. bottom #s really hard to read looks like 1943 40MM thats about all i can make out. Thank you!

[davejb]

Can you show us the base, from what your saying thats exactly what it is a 40mm cannon shell used i believe on a lot of anti aircraft weapons

[scottl]

I don't know if you need to see writing because I can't get that in picture as so faded but here is a picture of the bottom.

[davejb]

The base is a brass mixture which using a metal polish may remove the dirt and bring out the letters and no/s more, my main concern at the time was that this shell was in pretty good condition and some people have a habit of not checking the base to see if the priming cap is still in situ, it happens, ive seen it done and the aftermath, im sorry if im teaching you to suck eggs but a lot of GIs brought back live ammo and ordenance and some ends up on mantels as a display, try to clean the base and see what happens, please do not use any abrasives