Based on miscuts and uncut material, this is what I suspect the 5th series looked like. This is subject to change if I find some additional material, but it matches everything I know so far.
The leading card is shown in the left column. The boxes are my way of overlapping the various material which was used. Card 421 is a guess, based on a miscut of K
1966_5th_series.JPGaline found. card 375 position is now confirmed.