Seeger Retaining Clips.......?

Hi.

I am a newbie here and hope not to stand on anyone's toes.

So we have only used router spiral bit sizes up to 12.7mm shank and we are now looking at 16mm.

Really I have no experience with the bigger size tooling and have noticed retaining clips on some bits (14mm to 20mm) and some bits have the groove cut but no retaining clips.

Have attached a pic.

1.) What is the purpose of the clip on the end of the shank...? Does anyone have some data or info, technical drawings, even literature or something....?

Can anyone please help me out with the above...? Would be greatly appreciated.

I've seen in one particular catalogue that this is a 'Seeger' Retaining Clip BUT what the heck is it's purpose...?