hi i looked in the archives for "classic lenes" and wasn't really able to find what i was looking for and was hoping that someone might know at least where i might look for my answers.
i have 90mm raptar in a us army signal corps (rapax) shutter, and there is a "yellow dot" by the rim. for 12 years i have wanted to know, what the yellow dot signify? chromatic? apo-chromatic?