It's just over 4 inches and just under 11cm long: not unusably short, but not comfortably long, either. It's worth keeping for when I don't have a better pencil to hand, then.
You'll have noticed, though, that it has a notch cut into it. At school, kids often take stuff belonging to other kids, and as a precaution against anyone's stealing my pencils I used to cut a slice out of them with a modelling knife and write my name on the exposed wood. If you cut close enough to the lead, it means no-one else can take a similar modelling knife and shave your name off. You can't see my name on this particular pencil because of the ravages of time, but if you look closely enough you can see the line of the lead underneath. Later, I put the notch nearer the end of the pencil so it didn't get in the way when I was writing (not at the end, because then people could sharpen the pencil at both ends and get rid of it); that makes this a relatively early version. That's confirmed by the fact it's an HB; my later pencils were 2H for Technical Drawing (I was the only person of the 15 or so taking O-level Technical Drawing actually to pass). Well, I did have a 6H and a 6B, because that's as hard/soft as the pencils for sale in the local art shop went.
Basically, then, this is a pencil I had at secondary school. It's probably about 38-40 years old.
I think I'll still hang onto it, though. Who knows when I might need a pencil and not have a longer one around?