In 1986, the prototypes for Strf 9040 and Strf 9025 were ordered. Five prototypes were constructed but, before delivery in 1988, the 9025-version was discontinued. These prototypes were tested during extensive trials for three years between 1988 and 1991, during which the prototypes for specialized variants (FOV, C&C and ARV) were ordered.[3] The first deliveries started in 1994.