Lucky, lucky you. That has my favorite decals - Tiffany or Gingerbread. It
probably is a 115, but could be a 15 as I have found the "G" numbers are notorious for being messed up. Be careful with the decals. Clean per "sticky" in this forum about cleaning using sewing machine oil and cotton balls. It seems like it would attract dust but I have found it really doesn't and it won't harm the decals if used with cotton balls, and not "scrubbing."
For the manual, IF it is a 115. I would suggest
http://www.sil.si.edu/DigitalCollect...2683/index.htm On page 20 and 21 of this manual has the oiling and also an image of the underside of the machine. The 15 looks different.
Don't use the Singer site
http://www.singerco.com/support/instruction-manuals IF it is a 115 as the manual they have is NOT a 115.
Happy stitching with this beautiful machine.
Janey - Neat people never make the exciting discoveries I do.