The top row of Scott #9 is one of the easiest stamps to plate especially with the online tools available today. Having a pair with full margins makes it almost impossible to get wrong.
Starting with the Guide Dot Illustrations on Stamp Smarter,
https://stampsmarter.org/features/S...Plating.htmlThe ornaments at the top are full, meaning that it is from the right pane not the left, so we are looking for Plate 1 Right Late.

The position of the guide dots brings us to a match at 7R1L and 8R1L.
The double transfer of the top ornaments of the left stamp confirms the 7R1L position which is a premium position because before the plate was recut, that position in the early state of Plate 1 (position 7R1E) is where the rare Scott #5 comes from. Below is a picture from the Stamp Smarter database where I added arrows pointing to the most obvious elements of the double transfer. Compare those spots on the left stamp with the right stamp. That is a beautiful pair, I am envious.
Unfortunately for you, the right ball ornament at the bottom is incomplete which confirms it is a #9 and not a #5 although many other aspects of the stamp look just like a #5. (I have a copy of 7R1L in my collection in the spot for #5 (7R1E) marked as an 'almost' #5).
