Child restraint anchor points have a plastic cap screwed into them that needs to be removed first. In a W124 sedan or coupe they are on the rear shelf. In the wagon they are on the load floor between the second and third row of seats. This applies to Australian delivered vehicles although I understood it to be an internationally accepted system by the time the W124 was released.

__________________
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.