Mystery Piano Music Notation
I'm hoping someone might know what the [ symbol is on the attached example (Looks like a sideways bow up or down symbol). I've never seen it and would like to know what it's called. I've read the wikis and they don't even list this.
It's sheet music from 1963 and it's used twice in the piece.
Maybe someone will know what it is and let us all know. Thanks in advance.