Identifying the Crown.
The official designation is that one is the Tudor Crown (The Kings) and the other is the Crown of St Edward (The Queens) -thanks to Andrew Chaplin for making clear which is which as we can never remember!
When you have seen a few it is easy to tell a Victorian Crown from a Queen Elizabeth II one. There is, unfortunately, no way of distinguishing the different male monarchs by versions of the King's crown on their insignia.
Military exceptions to this rule include The Green Howards (Alexandra, Princess of Wales' Own Yorkshire Regiment) which use a foreign crown on their badge.
This rough method does not work with non-official items such as the marks on china.
The quick way to remember the difference is to think of the King's Crown as flat chested and the Queen's Crown as a matronly bosom. For those with a more respectable train of thought the Tudor Crown (Kings) is rounded and St Edward's Crown is the one with the double arch.
King's Crowns Examples ("flat chested") The Tudor Crown
Queen's Crowns Examples ("matronly bosom") The Crown of St Edward
Button, 1st South Durham Militia Showing Victorian Crown.
QE2 Hallmark. Sheffield.
Warning. This page is about British History so it remains true only until Mel Gibson and Hollywood bring out their own revised version where it will be shown everything bad is the fault of the English.