The 50 halala KM#68 (Schön#53) has 3 different types, as reported by Wolfgang Schuster.
Here you can see how year AH1431(2010) has a different calligraphy for 'khamsun halala’ (fifty halala) than year AH1428(2007):
The Arabic inscription 'khamsun halala’ (fifty halala) comes in 2 different forms regarding its calligraphy:
a) 1428H: the 'n' in khamsun is positioned above the u, and there are no diacritical marks below 'halala'
b) 1431H (and also 1434H & 1436H): the 'n' in khamsun is positioned left of the u, and diacritical marks are added below 'halala'
And in this second picture you can see that year AH1434(2013), and also AH1436(2015), has a straight position for year numerals, not like previous issues, that had a curved one:
So, finally, putting it all together, the 50 halala KM#68 exists in 3 distinct subtypes:
a) 1428H(2007): curved year, calligraphy type A for 'khamsun halala' without diacritical marks
b) 1431H(2010): curved year, calligraphy type B for 'khamsun halala' with diacritical marks
c) 1434H(2013) and 1436H (2015): straight year, calligraphy type B for 'khamsun halala' with diacritical marks
Image of the 1436H(2015) issue:
(information and images by Wolfgang Schuster)