Ecce is a partial deduction system which can be used to automatically generate abstractions for the model checking of many infinite state systems. We show that to verify the abstractions generated by Ecce we may employ the proof assistant Isabelle. Thereby Ecce is used to generate the specification, hypotheses and proof script in Isabelle's theory format. Then, in many cases, Isabelle can automatically execute these proof scripts and thereby verify the soundness of Ecce's abstraction. In this work we focus on the specification and verification of Petri nets