Come to think of it, may be you would get a good reticle if you are able to see a picture of what current japanese submarines are using today. From what I have seen so far, US Los Angeles class submarines still have in their scopes the same reticle as during WW2, and more or less the same happens with the russian and british submarines.
And in any case, even if it is different from the WW2 counterpart, it still will be positively from a japanese sub
Look at this, this one is a german reticle from the contemporary U-33 (Type 206 class):
http://1.bp.blogspot.com/_cys2T5FgJd...3%2Blaunch.jpg
And it looks almost identical to the WW2 reticle in the observation scopes (I have pictures of the manual of one of those scopes and can confirm that)