Don't know whether there should be a standard format for the no 4, but in a relatively short distance today, I've seen 3 different versions & several of each: a) the LH stroke is vertical b) the LH stroke is at 45 degree angle, but open at the top & c) LH stroke again at a 45 degree angle, but closed at the top.
All the 4s were the part of the 48, the Mugla registration no, so it wasn't down to regional variations.