It does appear to be an HI number. "14" is the model number in terms of quality; "8 1/2" is the length. I have no idea what the 5 meant, but it probably wasn't a line weight. AFTMA line weights weren't in common use until the mid-60's (it was adopted in 1961, but wasn't widely used for a couple of years.) If the rod was made before then, it's definitely isn't a line weight. And made after that, I would expect an 8 1/2 foot glass rod to be about a 7 weight. (There are a few more recent exceptions.)

If the rod is also marked with line size letters, along the lines of "HCH or D", they HCH part will mean a DT or WF line and the D will mean for a level line.