The basic rule is that an RAF Sqn has to have 25 years of service before it can be awarded a Standard. That rule has only been broken twice to my knowledge - a Standard can be awarded sooner if the Sqn in question has earned the monarch's appreciation for outstanding operations.
One of the exceptions was 617 Sqn (hence the privileged status?), the other Sqn was disbanded as part of the 2010 SDR and it's nameplate hasn't been preserved by being passed on to a training/support Sqn as is often the case these days.
Which equally privileged Sqn is/was it that simply disappeared? Answers on a postcard - or since most of my posts on pprune are ignored, maybe no answers at all......