Australia Multiple Dilemma

Happy Holidays everyone! I'm rearranging quite a few of my Australian Roo's and this one has always bothered me. It is the bi-colored 5 Shilling, which gives us the opportunities for multiple varieties:



The cancellation is 1 July, 1929 which limits this item to Scott 12, 44, and 54. (ACSC 42, 43, 44). The watermark is almost impossible to see, and due to the late date, I am leaning towards Scott 54 (ACSC 44). Retroreveal was not able to pull anything else out, so, to be honest, I can't see a watermark anywhere. However, Retroreveal did do a nice job on the back in showing me that it was laying on top of another stamp for much of it's life:



Now a scan of the back:



Then rotated and flipped:



Shows that we were sitting on top of a 2d King George V, Die I or Die II. I don't think we can tease out any varieties of that 2d, though, but it is fun to see.

Back to the front of my 5 shilling, it does look like an elongated Spencer's Gulf just below Roo:



Here is the picture from my ACSC:


So, please help out. I have a 5 shilling stamp with unknown watermark, unknown variety, and a pesky 2d stamp on the back. Any ideas on how to better tease out the watermark or confirm the variety? Thanks in advance.

You could just consign it to the stockbook, and get specimens with confirmed identities…

Partime,
Are you able to post a photograph of the front of the stamp with a strong light shining through from the back?

The best device I have scans through the stamp, but not with the brightest light. Here are scans through the front and back, but still tough for me to see. Maybe I should give it a good wash and remove the hinge fragment?

Partime,
3rd watermark might be in this location:

Well, I looked and looked. Sent it to Retroreveal in various stages and partitions, but I sort of see it, but really don't see it. I've got a lot of work planned for the next few days, but I'll revisit later. Thanks for your help.

Face down into some shallow water in a dark tray should also help identify it.

Partime,
Minor point....... I'm not so sure the 5/- Roo is a Bi-Color, for 60++ years 'Bi-color' uniquely referred to the Gem of the Roos, £1 Brown & Blue.

Finches,
The ACSC (Australian Commonwealth Specialists' Catalogue) indicates the 'Bicoloured High Values' to be the 5/- to £2 kangaroos, printed using frame (or duty) plates and separate vignette plates. The exception is the £1 grey, which was monochrome.