Another convention used on some early line printers left digit NUMBER@1 unornamented but added a tail or hook to the capital O so that it resembled an inverted Q or cursive capital letter-O -LRB- -RRB- .

And yet another convention common on early line printers left zero unornamented but added a tail or hook to the letter-O so that it resembled an inverted Q or cursive capital letter-O .
