As terrible as the kerning is for some of the axis labels, it may be a problem with a glyph substitution. I'm going out on a limb and guess this is from a PDF formatted file and it's possible that someone either embedded the wrong font or used a font that has an identical name to a later font and the glyph from the later font isn't what was intended.
A search indicated that this character may be used in musical notation as a time signature.
"In music, a C with a line through it is most often called “cut time” or “split time”, or alla breve."
It can also be the cent symbol for currency.
From some online locations I see that copying that symbol and asking Google about it says it is the cent symbol.