Welcome, the Old Town canoe with serial number 175439 is an 18 foot long, Guide model that was built on the Otca form with two and 3/4 inch planking, mahogany decks, a keel, and the stern seat moved two inches forward of the usual position. It was built between December, 1965 and January, 1966. The exterior paint color was G. S. (Guide's Special) green. It was shipped on May 26th, 1966 to Kittery, Maine. A scan showing this build record can be found by following the link at the attached thumbnail image below.
This scan and several hundred thousand more 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/catalogs/old-town/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-wcha to learn more about the WCHA and http://www.wcha.org/store/membership to join.
It is also possible that this could have another number or manufacturer if the description doesn't match the canoe. Feel free to reply here if you have any other questions.
Thank you for your very quick response. The information matches up to the canoe that I am looking at and the current owners were from Maine originally. I was not certain of the year of build and this fills in some gaps.