In the UK, cylinders under 500cc do not need testing.
As there is no test procedure under 500 it's not unusual to find custom cylinders with no date stamp, and there is no testing on the HFT or FT circuit.
There has been some date stamp checking at ISSF indoor events (10m pistol and air), i think they also follow the a 10 year rule.
BFTA/NSRA County Coach
CSFTA Chairman/BFTA Rep