There are 4 types, listed in Robson Lowe as follows:
Type 1: A long prong to the top right angle joining at an obtuse angle
Type 2: The prong on top left is securely joined to curl, then at right it is detached
Type 3: Both the above are detached and the βhookβ is present.
Type 4: The first βIβ of shilling if produced passes through the right limb of the first βNβ of βQUEENSLANDβ. In all other types this line cuts the first of second βEβ of this word.
I have interpreted this as follows:
The scans are 2 pairs = types:
12
34
Types 1 and 2

Types 3 and 4

I have no idea what the "hook" is in type 3. Is anyone able to explain it?
I have also done a table on the prongs but will need to check a number of examples to see if it is accurate.
Top Prongs
Type Left Prong Right Prong
1 Detached - short Attached - long
2 Attached - long Detached β short
3 Detached β short Detached β short
4 Detached β long Detached - long
I have also read that there are differences in the lettering for each type as well but am yet to explore that.
Also here are the bottom prongs, for what it is worth. I am yet to look at other examples to see if they are constant.
Bottom Prongs
Type Left Prong Right Prong
1 Detached - short Attached - long
2 Slightly Attached -short Detached β short
3 Detached β shortish Attached - long
4 Detached β short Attached - long
Comments and examples welcome
Thanks
Jeremy