The CWM has a few different captions for the destroyed gun. One caption reads:
Artillery Piece
Canadian soldiers captured this 77mm German field gun during the Battle of Vimy Ridge in April 1917. The German gunners rendered it
inoperable by destroying the muzzle.
Breech
Loading Rifled Artillery Piece CWM 19390002-221
http://www.warmuseum.ca/firstworldwa...aterials_e.pdf
Another reads:
A symbol of Victory
Canadian Infantry captured this 77 millimetre gun
during the attack on Vimy Ridge. It is unclear how it's muzzle was destroyed. One source claims that the German gunners attempted to destroy their own gun before it fell into Canadian hands, exploding a shell in the muzzle, but were killed before they could escape.
https://www.flickr.com/photos/sarge_...n/photostream/