This type of cloud is very difficult to properly identify as such even in this photo. In this photo, it looks like there`s altocumulus floccus at the top and altocumulus perlucidus just above the tree layer. These clouds look as if they are at different altitudes though both are well within the mid-level ranges (the photo was taken at dusk). In any case, this cloud had formed due to a shortwave at 500mb (indicated by a gentle dip in the 584 line) passing over the Maltese Islands. However, no thundery activity was observed. The weather sounding indicated various levels where altocumulus clouds could have occured hence the scenario for the formation of altocumulus duplicatus was quite plausible.