Actually there are 6 different backs. The first image shows the six different backs for the player cards.
I only have 5 different backs for the team cards which are shown as well. The group of 4 team backs were scanned in black and white but are the same colour as the others.
There are also many variations on the front.
1) player name (club).
2) player name (Club) and position,\
3) playername (Club), Captain, position,
Position is sonetime as example FULLBACK or FULL BACK,
Also seen Johnny Greaves card as Canterbury and as Canterbury-Bankstown
Seen Captain and captain for same player (small and uppercase C)
Also seen Some with printed signature and some without.
Hope this helps
Roger