In the VOLVO P1800 Jensen and the 1800S (1963), the end fitting of the static three-point seat belt is anchored below the window on the B-pillar.
The buckle is hooked into a bracket on the gimbal tunnel.
A belt that is not worn is hooked into a plastic button on the B-pillar.
Pos. 18 #660634 Button ch -4.378
Pos. 21 #669256 Hook excl. USA: CAN ch 4.379-20.999
Pos. 22 #672805 Button ch 21.000-23.487