Hi
That is a nice piece. There is a very strong likelihood it shipped in March, 1946.
The stocks are the prewar style. Some early postwar M&Ps shipped with that style stocks, but they appear to be all gone by about mid-April, 1946, replaced with the postwar style having a more restricted pattern of checking. Both styles had the sharp shoulder. I will post a picture for comparison at the end of this text.
The washer is common on the prewar style stocks and on some early postwar style Magna stocks. Sometimes they are blued and sometimes in the white, like yours.
You were correct to notice the difference in the stock style. Good eye.
The sideplate on the M&P, beginning in the V series in December, 1944, had to be machined differently to accommodate the new sliding hammer block safety. To simplify the job of fitters, sideplates with the appropriate machine work were marked on the outside rear with the small S. A few months after the S prefix guns started shipping postwar, the S disappears, since by that time all the sideplates had the newer machine work, the older type having been used up.
I hope this clarifies matters for you.
M&P Grip Question
Linear Mode
