This picture was sent in recently with a query about its origin.
What you have here is the base of a 4.5 inch shell cartridge. The full cartridge was about a metre in length and was made of solid brass.
During a firing these cartridge casings were left over from a shoot and those that did not roll over the side were gathered up and either returned as scrap brass or as in this case turned into souvenirs. What you have here is a souvenir ash tray made in 1964 from a 4.5 inch brass cartridge used in the guns of HMAS Vendetta. This HMAS Vendetta served with the Royal Australian Navy 1958-79.
The piece sticking up in the middle contained the percussion fuse which ignited the surrounding cordite which became the propellant for the 4.5 inch projectile which was fired on the target.