Originally Posted by BMCM

That plate... the Firing Pin Safety Lever Spring Retainer p/n: 067940000 does not apply to any 9mm model, it is only found on the forties, 10mm and 45 guns.

Your gun, M5946, lacks that plate so the only thing holding the two springs in place is the sight base.

Even more care is required when re-installing the backsight. You must drive it on part way then carefully tuck the firing pin safety plunger spring under the sight base... Then continue bumping the sight on until you reach the ejector depressor plunger spring on the other side, tuck that spring under the base and continue.

Go slow and pay close attention, it's quite easy to pinch a spring between the sight base and it's recess in the slide and either mangle it or shear it off right proper.

Cheers
Bill