Let's start with the type designation: As it is an LF 8, i.e. a fairly light fire engine, the 90 hp already fits. According to Mr Regenberg, it was available in the
S 3500 / Sirius and in the S 4500 / Mercur.
The puzzle LF 8 was built three times in 1954 by Jacobs & Sohn in Neunkirchen, Saarland. One example ended up in the Prora Railway and Technology Museum on the island of Rügen. See photo.
We have a Mercur 125 FA, built in 1959, in our fire brigade as a traditional vehicle. We received it from our twin town in 1991 and it was only decommissioned in 1998. From ‘96 to ’98, I drove and operated it on several missions. Second photo