That is either a 52 or 52E.....the easiest way to tell is if you can post a clear pic of the spark coil inside the recoil I can tell you for certain. Not a 521 either.....very similar but the flywheel side case half and recoil cover is altogether different than the 52/52E and it also has an alum flywheel/fan as opposed to the black plastic fan of the 52s.