The Renault YS 2 was an artillery observation vehicle with advanced telemetric optics, among which a rangefinder turret. On 20 July 1936 it was decided by the Artillery to acquire such a type, called the "voiture blindée tous terrains d'observation d'artillerie". On 11 August Renault was contacted to build a full scale wooden mock-up of a vehicle capable of accommodating the ER26 ter and R14 radio set, a large number of telephone cable connections and on top an optical rangefinder turret with a base of 160 centimetres. The Renault tank design bureau estimated that such a mock-up could be created for the negligible sum of just 6500 French franc and thus on 21 September made the counteroffer to rebuild one of the YS prototypes for ₣ 195,000, apart from supplying the mock-up for ₣ 9500. However, the ministry of defence refused this offer, just ordering the mock-up on 12 October.