The shoulder eagle is not a formation sign. It was worn by all RAF Airmen but not by Officers. Only the very early (1918) eagles had round corners at the top. Throughout the rest of their life they have always been rectangular. However those used by commonwealth air forces were rounded at the top if they also contained the country identifier. All eagle badges were in "handed" pairs ie. one flying right and one flying left. They were worn so that the eagle faced rearwards. Australia was the exception with all eagles flying right.
During the war there were many variations worn by dominion countries according to where they were made which is why the one you have seen is different to the one I illustrated. See my album at for examples of different eagles.
https://www.britishbadgeforum.com/fo...p?albumid=1234
The price of £2 is OK although you can get better versions than the items you have.
Hope this helps.
Dave