It is for marking 5mm copper tape. But I can't tell you what scale it corresponds to exactly. What I think is possible to remove one of the sprockets for narrower copper tape.
Wow!
What smart little tool that is.
As for scale, my model shipways kits that are copper hulled, are supplied with 5mm tape and they are mostly 1:64. The exception is the constitution, which is 1:76.
As for fidelity...who knows.