The ENTAC (Engin Téléguidé Anti-Char) portable infantry weapon first entered service in 1957 but the earliest record I have located indicates that it was not fitted to M201 jeeps until 1963. I suspect that relatively few jeeps were converted at this time for evaluation. A decision was subsequently taken to replace the SS 10 missile system with ENTAC and more jeeps were converted to ENTAC carriers by the ERGM La Maltournée workshops in October 1966.

ENTAC (or MGM-32A) was a wire guided missile system (note spelling mistake below) controlled by an operator safely away from the jeep. It was not a good idea to fire the missiles whilst still sitting in it.

  Unlike the SS 10 and 106SR, ENTAC did not require the jeep it was mounted on to have the back panel cut away. The war in Algeria ended in 1962 and with it the need for large numbers of the Sahara version of the M201. As the Sahara had a reinforced chassis and suspension most of them were converted into ENTAC missile launchers from 1963 onwards.

Conversion of a Sahara was fairly straight forward as the launcher assembly bolted on to a standard body tub and a complete rebuild of the jeep was unnecessary, though to support the extra weight, coil springs were used to reinforce the rear suspension. The original registration number was retained. 221-2291 (in the photo) note also the Sahara spot light still mounted on the windshield though the air pre-filters were always removed..

ENTAC was in turn superseded by the second generation MILAN missile system in the 1970s and the workshops at La Maltournée spent the three years converting jeeps to carry the MILAN before closure in 1978 .

Consequently as ENTAC jeeps were withdrawn they were not rebuilt and the missile equipment was simply removed at other workshops, e.g. ERGM at Clermont Ferrand, leaving holes in the rear wheel arches which were simply covered over by a plate riveted in place.

The photo is of Tim Tearle's M201 which has the full history of being a Sahara which became an ENTAC launcher before being returned to standard use.

A further piece of ENTAC evidence that could be lurking underneath your M201 is the bracket shown in the photo below (also of Tim's jeep). It is identified in army document BT 603 as being a support for a 'coffre à chaines' (box for storing chains) on an M201 ENTAC.
2009 saw the appearance of a new exhibit at the musée des blindés (Tank Museum) at Saumur in France - an M201 ENTAC.
I am grateful to J-L Martin for providing copies of the official data sheets used on this page and the two photos above from Saumur. The next page contains a more detailed look at the ENTAC system and the Saumur exhibit.