1942 ver. FM 23-7 and adjustable sight

Anyone else notice that in the 1942 version of FM 23-7 that it shows, starting on page 12 of the PDF, a fully adjustable rear sight? Apparently it is the one under development before the type 2 was issued. It looks like a cross between a Garand and Type 2. Blow the PDF up to 200% and you will see what I mean.

I have read somewhere that there was an adjustable out there for field trials, but it was not entirely successful. Maybe the field trials included actual combat usage, just as the 6.8SPC M4 has seen in Afghanistan.