@Akira: judging by the shape of the breechend, and the ammunition shown, this must be a 17 cm S.K./L 40.
There were not that many 17 cm S.K./L 40 guns along the Channelcoast, so you might be able to trace this picture back to it's specific location, i'll see what i can find out.
Additional info about the ammunition, and some pic's can be found here:
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