First aid kit No.4
 Trousse de Première Urgence N°4

  First aid kits were fitted to US army jeeps from mid 1943 onwards but were only fitted to one in every four vehicles. The kit was held in a bracket mounted behind the dashboard between the instruments and the glovebox.
The photo opposite shows clearly the four mounting screws used to secure the bracket. I have not seen an M201 with a first aid kit bracket fitted in this position or even the four tell-tale holes, but if you have then please let me know.  
The early post-war No. 4 French Army first aid kit for vehicles (shown below) was almost identical to the WW2 American kit in the same box but with French writing. It is probable that these kits were of American origin like much early post-war French Army equipment.
A later 1965 pattern box for the No. 4 kit (shown below) is slightly larger and has a carrying handle at the side rather than at the front. In case you're wondering, 'secourisme' is a directly translates to 'first aid'.
As far as I can tell the last two digits represent the year of revision for the particular kit and its contents i.e. 1950 & 1965 examples above and 1986 & 1993 examples below.
The 1993 pattern kits were assembled and packed by E.R.M.M. at Ardentes (36) for the SERVICE DE SANTE DES ARMEES (SSA) in the case of my example and the contents itemised in the document below.
According to MAT-3943-1 each M201 included a set of tools, accessories and spares but the items listed did not include a first aid kit. This probably explains the lack of a mounting bracket. It seems likely that first aid kits were carried in some jeeps but it seems probable that it was simply stowed away in the glovebox or in one of the rear lockers. If you have any further information on this please e-mail me.
One final point to be made is that, just because a first aid kit has French writing on it does not necessarily mean that it must be of French army origin. The final example has both French and Dutch labelling and is actually Belgian army issue. The box is otherwise almost identical to the one above.