Just call S&W or Earl.
I just found this posted by Airfix....
From Germany:
"The PPS sight is drift adjustable. Drift adjustment is done with a hammer and a drift punch.
Sorry about that, but there is no screw or anything to assist adjustment for windage."
There is a T-cut at the rear sight channel, that is to facilitate the installation of the rear sight, sliding it from right to left. I have a close-up picture for that, but too large and unable to upload here.
Airfix