The 'hole' is right about where the hammer axel pin seats into the right side of the frame.
Maybe(?) the mechanic was going after that area for some unkn reason.
Pretty close,,eh,,good enough.
Looks like a Black&Decker performance but the entire idea would be classed as something not even worthy of thought in most peoples minds anyway.
The next step to fixing it may have been to spiff that up by pounding a Lead ball into the hole then smoothing it off w/a Dremel. Leaves it kind of shiny lookin' and it'll match pretty good.
Bubba et al