Here's the obverse of a Kuwait 20 Fils with the date AH1390-1970, which isn't listed in my copy of KM.
It weighs 2.95g; I have a 1974 that weighs 3.03g. KM show the weight as 3g.
They list 1389-1969, 1389-1970, 1390-1971, 1391-1971.

So is mine especially rare, a forgery, or just missing ?
Have you got one too ?