That last reply didn't sound very helpful unless one is really used to pulling cameras apart and working on them.
If you are trying to adjust the rangefinder for infinity then surely you remove the screw on the front of the top cover between the viewfinder objective and the illuminating window to reveal a tiny adjustment screw whose slotted head is not necessarily in line with the hole of the covering screw, and may be set in quite deeply. This is where the horizontal(infinity) adjustment is in my Yashica YF, which is just a continuation of the Nicca LTM copy family. I have only seen photos of the Nicca IIIL in Hans P Rajner's book, Leica Copies, but I would assume the vertical RF adjustment is under the round bezel on the front.