Wayne: I'll give you the build records for both serial numbers you've provided. The Old Town canoe with serial number 45901 is a 17 foot long, CS grade, OTCA model with birch decks, thwarts and seats. This canoe has half ribs, a keel and outside stems. It was built between October 1916 and March 1917. The original exterior paint color was orange. It shipped on March 31, 1917 to Harrisburg, PA.
The Old Town canoe with serial number 45907 also is 17 foot long, a CS grade, Charles River model with maple decks, thwarts and seats. This canoe has a keel and a floor rack. It was built between October 1916 and April 1919. The original exterior paint color was bright red. It shipped on May 8, 1919 to Portland, Oregon. The OTCA (45901) will have longer decks which could also help ID the canoe you have. Pictures would be helpful if you can not identify the canoe from this information. Scans of these build records can be found by following the links at the attached thumbnail image below.
These scans 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/wcha/ to learn more about the WCHA and http://www.wcha.org/join.php 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.