You're right about the SFS being made by Cylinder & Slide. They had 2 FN Hi-Powers, one used (850) and one new (999) and both had the SFS on them. Those prices seem really high to me, just like all the guns around here lately. I was more curious why an aftermarket part by C&S would be on a new pistol.
"The Constitution shall never be construed to prevent the people of the United States who are peaceable citizens from keeping their own arms."
- Samuel Adams