76.2 cm L/30 WagenFlak Rheinmetall (russ 02)
Contribution :
Bernard Plumier
WW1 artillery blog link
Location :
Belgium
Brussels
Army Royal Museum
Another ultra-rare item in this incredible MRA museum, since it seems only 4 such variants of the Rheinmetall gun have been built !
View on the compensating piston
The Russian fieldgun tube and recuperator are easily recognizable