New Zealand Postal Fiscal Problem Of Identification

Collectors, please. I am stuck again. I show scans of a two-pound New Zealand postal fiscal for which I cannot determine the watermark. I have tried retro-reveal and picture-manager and can see nothing. When I breathe on it, it curls from side to side, which makes me think it the paper is vertically laid and that the stamp is therefore either the 1937 or the 1946 issue. Both are bright purple. The 1937 is described by Gibbons as SG F182 "thin hard Wiggins Teape' paper; the 1946 is described as SG F206 on "Wiggins Teape chalk-surfaced paper.
I tried the silver test and got no mark. The paper feels stiff but not particularly thin. I show a small section of the back at 600dpi. Soory it is there wtice and I have not found how to remove the duplication

My questions: how can I identity which issue it is. Can anybody help



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Michael, sorry I can't help with your main question, but maybe I can on the above quoted question.
To remove that 2nd pic, click edit (3rd inon from left, pad of notepaper and a pencil) and backspace the last link out. Post changes.

Thank you, Littleriverpill
Michael