The Jaguar schnellboots were the previous class. The "Dachs" photo is a Zobel class type 142. It could look confusing to some because the more common model Zobel's are the upgraded versions, type 142A. The difference between the 142 and 142A is significant. (Graupner started production of the 142 version but upgraded the kit to the type 142A soon after the real boats were upgraded.)
I bought my 142A in London in 1975, started it then stored it. After 2000, I decided to finish it but that took another 10 years as the internet was now available - and so was information on the real boats. Nothing like starting all over!
Probably not a build time record, but it did take over 35 years from purchase to running.