It’s this, which looks like a G with a (broken) bar through it:
but it should be a C with a bar through it (broken or not I suppose is a stylistic choice):
The gray glyph is drawn by the system. it works correct in 10.7 and 10.10. So I don’t now where your problem is coming from. Maybe you have a font installed that the system picks instead of the system font and it is not correct.