I may be able to solve the mystery of your other canoe. The Carleton canoe with serial number 19271 is a 17 foot long, CS grade, Carleton model with Western red cedar planking, open spruce gunwales, birch decks, birch trim, half ribs, a keel, outside stems, sponsons, and a bang plate on the full length of the keel. It was built between October, 1925 and April, 1926. The original exterior paint color was orange with a 5/8"(?) black stripe. This may have looked similar to the one at
http://www.wcha.org/catalogs/old-town/designs/design20.gif that was known as the Old Town design number 20. It shipped on May 8th, 1966 to Scranton, Penna. A scan of this build record can be found by following the link under the thumbnail image attached below.
The 15918 is a more difficult puzzle. Kennebec shipped an 18 foot canoe with this serial number in 1922. The Carleton and Old Town records for this number don't show a 16 foot canoe either as Ric mentioned previously. I would encourage you to review the information at
http://www.dragonflycanoe.com/id/ to see if you can identify your canoe's manufacturer from any other characteristics. It might also be helpful if you could post some pictures and confirm the dimensions. The information at
http://forums.wcha.org/showthread.php?t=791 may also help. There is always a possibility that the length was recorded improperly on the card but this is not likely since several people would have reviewed this through the process of construction and shipping.
This scan was created with substantial grants from the Wooden Canoe Heritage Association (WCHA) and others as you probably know well. Additional information about 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/wcha/ to learn more about the WCHA and
http://www.wcha.org/join.html 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.
Benson