I believe you have a 115 from about 1918. A manual for the 115 from that time period can be found at
http://ismacs.net/singer_sewing_mach...ine-manual.pdf The manual for 115 on the Singer site is for a later machine from the 1960s, I believe.
Leon, is right about the stickies
Cleaning and repairing the Shellac clear coat on Vintage sewing machine heads and
How to Clean Up and use a vintage sewing machine - videos by Muv and Fav
Also, about it not being that bad. I have used Nev-r Dull, Brasso and 0000 steel wool on some metal pieces that have been removed from the machine. I have
not been able to get pieces to shine up to bare metal again after using Evaporust. I have used a dremel and metal polish, which will protect it, but still dark grey after Evaporust.
Patience and care will bring it back to functionality. A new belt would be in order.
Janey - Neat people never make the exciting discoveries I do.