Is There An Easy Way To Tell The Different 1911 To 1912 KGV

I am not an expert on Great Britain stamps. The King George V stamps of 1911 to 1912 have several varieties according to Scott's and even more according to Stanley Gibbons. I go by Scott numbers. I have found the One Penny's easy to tell by the shading on the Lions. Is there a simple trick to the 1/2 penny's? I know Scott's goes off on details and often there is a much simplier way, like the flick of the paper on 3 cent green banknotes.
What would be great is a detailed example of each. Once I can tell the re-engraved from the originals then it should be just a matter of the watermark,...... I hope.

Here are the two stamps ,let me look around and find two better copies which show the fish scales better .

Pjsstamps, everything you wanted to know about Downey Head stamps can be found in this excellent thread by Skilo54:
https://goscf.com/t/12112&SearchTerms=Downey,Head

Detailed instruction on the 1/2d stamp can be seen on page 8 of the thread.

Here is the S.G. specialised stamp catalogue

Wow mhc99, that thread was just what I was looking for! Now I have a huge pile of stamps to go through.
Thank You