Hi Duncan---Well, this is a mystery...
The serial number on your canoe certainly appears to be 117428--- this comes up an 18 foot GS (lowest) grade guide model canoe with white Maine cedar planking, open spruce gunwales, ash decks, ash thwarts, ash seat frames, half ribs and a keel, that was shipped to Naples, ME, on June 23, 1936.
This doesn't seem to me to be the correct record for your canoe. The lack of half ribs is an obvious difference, as are the presence of outside stems, and the small carry-thwarts, which-- if this was built by Old Town-- would indicate the canoe originally had sponsons.... unless the original owner specified wanting them. Look on the inside of the canoe, along the sides, to see if there are any tell-tale holes where screws might have held sponsons. Seems to me that adding carry thwarts without sponsons would be something that was noted on the record (along with the OSS).
Where are the decks? If this is an Old Town, it's been scalped! Poor thing.
Maybe someone else has an idea of what this canoe could be, if not an Old Town... and meanwhile, I'll look at the records for a canoe that fits... I'll try some other numbers.
The scan for this record is attached 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 anyone reading this will join or renew 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 renew.
Kathy