When the original M and S where introduced each manufacturer had a proprietary light rail system.
Walther/H&K/Steyr/Sig, and a few others.
Laser Devices made and still makes lights in almost all of the sperate mounts EXCEPT the Steyr mount as the gun was discontinued before it gained enough popularity.
Now there is a Universal light mount that Steyr/Glock/Sig/Kimber/Beretta and others use.
There was/is an adapter available for the M series rail attchment but it is a bit ungainly.