There is no standard way of ranking and no defined meaning for levels.
Wrong. Put simply, they're the number of ways the firearm is "actively retained," meaning the wearer must do something specific to defeat that means of retention. Friction doesn't count, so the old-style leather holster in which I carry my 1851 Navy Arms .44 caliber cap and ball black powder revolver would be considered to have a retention "Level 0."
IF with an attacker's hand Only on the grip of the weapon it takes less than 5 seconds to trip/flip/rip/rotate/prestidigitate the firearm from the holster then it's Level-0.
That's one way of stating it, although I would argue the "5 seconds" is highly arbitrary, and therefore not any sort of a "standard."
I submit the following, from a common law enforcement manual:
Levels of retention
The retention level of the holster refers to the number of retention devices you have to release or move the gun past in order to draw the pistol from the holster:
An example of a level l holster would be a simple thumb-break device that must be unclipped in order to draw the weapon.
A Level ll holster example is one where a thumb-break is released then the pistol must be moved (rocked forward or rearwards) in the holster to clear some form of internal locking device before it can be drawn.
A Level lll holster is one where three separate retaining devices, both internal and external must be undone or bypassed. -
The questionnaire should have been:
Level 0 (no retention except friction)
Level 1 - One means of retention
Level 2 - Two means of retention
Level 3 - Three means of retention
Other
I haven't a clue as to what "Level 4" might be. A padlock? Lol...
Thus, to answer the OP's question, my tactical holster has Level 1 retention.