If it is a hyperfocal focus mark then there may be a matching mark in shape or colour on the focus distance scale and aperture ring. If it was an infra-red adjustment mark it would be on the aperture mark scale only, around the near side f4 tick. I doubt very much that it is for infra-red.
I have a 35mm Voigtlander with a triangle and a circle mark on the focus scale, one for near zone focus and the other for hyperfocal length. The apertures are not marked, but you can see which is intended because it is adjacent to the infinity mark on the hyperfocal setting.