This bargain basement find of auxiliary lenses is quite a joy for me. First, I was
not aware that Petri made such a set, and second, they were in as new condition,
with case. They simply screw to the filter thread. Although not marked for focal
length it seems the aux. telephoto is actually about 90mm equivalent, and the wide
angle 35mm, which would be a match up for the common lenses of the Leica and
Canon RFs of that time. I expect they will not be too sharp; perhaps a little 'Lomo' even.