Canoes that are that light are usually race boats. They're called C-1 or C-2. Today they're made of Kevlar or carbon fiber and go +or- 20 lbs for 18 ft. Yours may be an early pre-Kevlar version. If this is true the boat should be used with care. Racers are in a hurry and aren't adverse to bouncing their boats off of convenient rocks.
Even if it isn't a racer the lightness precludes heavy loads and boney water. The comments already posted are right-on. Check for flex cracks (even Kevlar canoes get these) and pretty it up with a coat or two of epoxy. Epoxy is subject to UV degradation so the hull should be covered with a suitable spar varnish.
Whoever built this boat was ahead of his time. 'Glass canoes with wooden ribbing are still being made. Navarro is one manufacturer.
Lightweight 'glass recreational canoes oilcan badly and pretty wooden ribs are one way of solving the problem.
Keep us posted.
Charlie

: Well, I've now seen the boat, and it is not at all what I pictured. This is
: essentially a fiberglass shell, made over a form (then popped off) with
: polyester resin, only about 1/8" thick. It then had steamed ribs
: sprung into the shell, perhaps every 10 inches, and then connected with an
: outer keel, inner keelson and inner and outer gunwhales. The ribs seem to
: have been bonded to the shell with some sort of adhesive which in many
: places is giving up so that they still conform to the shape but don't make
: a perfectly tight fit. The boat only has a varnish finish on the woodwork,
: but nothing on the shell, so, as you can imagine, is completely
: translucent. I wonder about UV damage (is polyester susceptible to the
: same effects of UV as epoxy?), and also if the shell is becoming brittle
: over time. It seems to still have some flexibility, which is alarmingly
: evident in the ends where there are no ribs for the final 18 inches bow
: and stern. The entire boat, about 17 feet, weighs all of 25 or so pounds.
: Clearly not for extreme conditions, but it seems to have stood up to
: healthy use over the past 25 or so years. Anyone seen a boat like this
: before?