An illustrated event cover for the Pompeii exhibit at the Royal Academy of Arts. The exhibit ran from Nov 20 1976-Feb 27 1977. But according to the below cancel, it appears to have been extended? 

Here is a last day pseudo-cancel that was applied to same cover as above, "...Posted on last day of Pompeii Exhibition" dated March 14th 1977. 
Thank you Tiem! A Pompeii view on center 2002 Vienna UN administration stamps
The sender of the card stated the obvious and wrote in 1929, "Pompeii on this picture was certainly old."
Beautiful card from the grand tour posted in 1903! Vesuvius looking ominous in the background.