I'm looking at a hand-written score (with terrible handwriting) and I see something that looks like "upbow" (?) but it is between notes, and in a score without strings other than piano... It's a small "V" or check mark on the top-most staff line, and appears for SABT and bass and treble clef of a piano.
Elsewhere in the score is an "apostrophe" breath mark. So, I don't think this "V" is indicative of that, but given the quality of the hand-scrawling, it could be...
(I only see one "apostrophe" style breath mark. Perhaps the "V" is a different kind of breath mark?)