20Pdr with the smoke projectile (Unfired but deloused) pretty nifty having an intact driving band as they are usually engraved with rifling or taken off as allot of WWII & WWI gear due to copper shortages.
The projectile itself is very long when shown next to the 20Pdr APDS projectile it's pretty hefty as well the 303 Mk VII round is for scale.
I don't know its burn time perhaps some artillery chap's or Tankers who operated the Centurion may know.
It is another one in my collection that I really like.