This looks much more likely. The Old Town canoe with serial number 173681 is an 16 foot long Otca model with half ribs, a keel, and sponsons. It was built between February, 1964 and September, 1968. The original exterior paint color was dark green. It shipped on September 29th, 1968 to Bangor, Maine. A scan of this build record can be found by following the link at the attached thumbnail image below.
Feel free to reply here if you have any other questions.
Benson