Welcome and congratulations, the Old Town canoe with serial number 183881 is a 16 foot long guide model with a keel. It was built between September, 1969 and January, 1970. The original exterior paint color was dark green. It shipped to Salem, New Hampshire on May 4th, 1971. A scan showing this build record can be found 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 donate, 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
It is also possible that you could have another number or manufacturer if this description doesn't match your canoe. Canoes with a family history are always extra special. Feel free to reply here if you have any other questions.