The Carleton serial numbers stop in the 20,000 range as shown at
http://www.wcha.org/catalogs/carleton/carleton_chart.html so my guess is that you have an Old Town canoe. It may have shipped as a Carleton in the rush to fill an order. The Old Town canoe with serial number 68402 is a 16 foot long, CS grade, Charles River model with red western cedar planking, open spruce gunwales, birch decks, and a keel. It was built between December, 1921 and June, 1922. The original exterior paint color was probably similar to the image at
http://www.wcha.org/catalogs/old-town/designs/design13.gif which was know as the design number 13. It shipped on June 13th, 1922 to Geneva, New York. A scan of this build record can be found by following the link at the attached thumbnail image 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. The long decks are not mentioned on the build record so those may have been added later. Feel free to reply here if you have any other questions.
Benson