It looks like you have a "Rebuilt" Singer 27 machine. I think it may have been rebuilt in the 1940s. The machine itself would have been made in 1891. There were several companies that would rebuild machines by putting a crinkle finish on them. Also would put a motor and probably light on. Like yours, sometimes they would add a reverse device and/or quick release for the pressure regulator. I think those features on yours are probably Revco parts.
There is some good info about this practice at post #4 at
Great Eastern Rebuilt Singer
Janey - Neat people never make the exciting discoveries I do.