Help with G3 ID

[Porsche!3]

I have recently purchased a NIB G3 (photo enclosed). The receiver is marked G3 FS. I am confused in that it would appear (or possibly I am confused) this designation is for a non-full auto weapon, whereas the rifle clearly has a "SEF" trigger group. I am also not familiar with the small lever and the adjustment screw just behind the trigger. This is a H&K weapon made in Germany in 1978. Any help will be appreciated.

Best regards,

[Porsche!3]

I have identified the weapon as a G3SG/1.

[max popenker]

Yes, it's designated marksman's rifle G3SG1, the small lever is used to set trigger for accurate shooting in semi-automatic mode