Kienzle board clock BoUK2 FL23886-1

[Theodor]

Gentlemen, can you please tell me, on what aircraft was used this clock? From what I know so far, it is quite an early model, was used on multi-engine aircraft. But what models exactly?

The clock model is: Kienzle BoUK2, Fl number 23886-1

Thank you very much in advance!