The base that attaches to the rifle shows signs of casting on front and rear edges, so it did start life as a casting. The rest is nicely machined, and to such a close fit that even when the securing knob is loosened, the sight and the base have no play between them.
Did the Win. 52 use vertical mounting screws? Thought they were horizontal? And since the back of this sight is flat, and appears to have not been thinned, I'd guess the sight was for a flat sided receiver like a Martini, or one of the old lever guns from Marlin, Winchester, etc.
