Thomas Baumgärtel aka Bananensprayer from Cologne is marking galeries, museums and other arty places with his approx. 4,000 spray-bananas since many years and in plenty cities in Europe and beyond.

https://bananensprayer.de/kunstorte

In Hamburg you can find them at Affenfaustgalerie, Fettstr. 7A (back yard) and HWF Galerie in Bernhard-Nocht-Str. - not sure wheater all are originals, as the last one is a paste-up.