Italian seaplane training units were based in the Pola area - Portorose and Puntisella - and I don't think that KG 26 units ever operated from there.
All Gruppen of KG 26 were based at time, in 1943, at Grosseto airport in order to train in the torpedo bomber role. The skyline of the mountains in the back of the picture is similar to that one visible at Porto Santo Stefano, in the Argentario promontory, about 45 km from Grosseto.
https://pensione-week-end-porto-sant...o.hotelmix.it/ (41 foto)
In that village a depot of the Regia Aeronautica was located so I think that it's possible that the picture was taken there.
According to Gregory Alegi the aircraft should be a S.16 ter (very similar to the S.59, development of S.16). In all pictures of the S.59 I've seen, this seaplane wore a silver paint (just like the CZ.501).
About post #7. I don't know any publication about aircraft employed in staff flights. Some figures about aircraft in charge are contained in the volume 10 of the serie "dimensione cielo" devoted to training and liaison aircraft.
E.g., in march 1942 the Gruppo Autonomo di Volo of the 2a Squadra Aerea (Padova) had 13 G.8 on charge and the 3a Squadra Aerea (Roma Centocelle) 6 G.8; one G.8 was with the Comando Aeronautica Albania at Tirana.
ciao
Gianandrea