In the Priest's Wood
A French dud munition (28cm)

An unexploded French ordnance can be seen in the foreground, the text claims it as 28cm meaning it likely is a shell from the Mortier de 280 modèle 1914 Schneider, a French siege howitzer of the same caliber.

There is German on the back of the postcard I am unable to transcribe as I do not speak German, see more in the source link. Posted 28 August 1915.