The 'original' GSM was issued twice IIRC first pre WWII and secondly post WWII up to Dec 1962 when Brunei was the last clasp. Not sure how many clasps were issued for both.
When one was first at the Secret Hampshire Helicopter Base, the PRO was an aged, bald, monocled RAF Regt Flt Lt with lots of ribbons - unusual in them days.
He (correctly) wore his pre-'62 GSM
in front of his war medals, which looked most odd and confused a lot of SWOs!
Think the bar was Palestine in the '30s......
[just Googled it - Wiki says "Palestine" bar was 19 Apr 36 - 3 Sep 39. Think we can work out why THAT closing date was used! Wiki also says 17 clasps for that one (7 before and 10 after WW2) and 13 - including the rare "South Vietnam" for the 1962 version.]