Are you sure of the number 18? Check the number as stamped into both stem ends.
The Old Town canoe with serial number 137236 is a 16 foot long, AA (top or premium) grade HW (heavy water) model with red western cedar planking, open mahogany gunwales, mahogany seats, decks and thwarts, and equipped with a keel, floor rack, and sponsons. It was built between April and June 1943. The original exterior paint color was light green, and was lettered G.A.F. on the right and left bow. It was shipped to iron River, Michigan on June 14, 1943. A scan of this build record can be found by following the link behind the thumbnail image attached below.
This scan and several hundred thousand others were created with substantial grants from the Wooden Canoe Heritage Association (WCHA) and others. A description of the project to preserve these records is available at
http://www.wcha.org/ot_records/ if you want more details. I hope that you will join or renew your membership to the WCHA so that services like this can continue. See
http://www.wcha.org/about-the-wcha/ to learn more about the WCHA and
http://store.wcha.org/WCHA-New-Membership.html to join.
It is also possible that you could have another number or manufacturer if this description doesn't match your canoe. Feel free to reply here if you have any other questions.
Greg Nolan