O-Ring 23 mm on fuel tank lock

[sneakyhuib]

Does anybody know how this 23 mm O-ring i marked with red is supposed to be positioned?
Its from a 1978 Honda CB750 K7

Greetz Huib

 

[hinksy]

I have an F2 with the same setup ( tank flap ) and I`ve got to say that I dont have one and I didnt know about it till now

 

[Loki]

Same here with my F1