Welcome, the Old Town canoe with the serial number 172428 is a 16 foot long Otca model with a keel that was built between September and October, 1962. The original exterior paint color was dark green. It shipped on May 3rd, 1963 to Klamath Falls, Oregon.
The one with the serial number 188881 is a 20 foot long Guide model with half ribs and a keel. It was built between March and April, 1972. The original exterior paint color was dark green. It shipped on April 21st, 1972 to Eugene, Oregon. The back side shows that the warranty card was returned from Seattle, Washington on April 23rd, 1973.
Scans showing all of these build records can be found below. These scans 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
https://www.woodencanoe.org/about to learn more about the WCHA and
https://www.woodencanoe.org/shop to donate or renew.
It is also possible that you could have other numbers or manufacturers if these descriptions doesn't match the canoes. Feel free to reply here if you have any other questions.
Benson