91 troopy

THIS

Mine are used as the centre supports for the tow bar on my 79series.

You may be referring to the 4 bolt holes left where a towing loop is fixed.There is normally a plate bolted to those holes with a towing loop fixed to the plate.It may have been removed by a previous owner or stolen.

Originally it would have had a loop type recovery point.
As Phil said it is the centre attachment for the hayman reese type hitch, the bolt spacing is also standard to fit a pintle hook type tow hitch.

I was at the local takeaway tonight and in front was a troopy with the ring bracket still bolted in place....I suppose people remove them as they might interfere with the step as you got in or out.
We get new model toyota's at work all the time but this the first time I have seen this ring bracket fitted.