The Singer 31-15 Industrial sewing machine. - YouTube
Singer 31-15 Sewing machine | BladeForums.com
KUNPENG - New Sewing Machine Bobbin CASE for Singer 31-15 331K CONSEW 30 130# BC-31-15=62740 (2) : Amazon.ca: Home
In Stitches - Singer 31-15 (c. 1915) in a custom treadle... now available. The 31-15 is a tailor's machine and capable of doing rather heavy work just as well as it will
My Refurbished Singer 31-15 - Leather Sewing Machines - Leatherworker.net