Historical, a fortress gun mounted at Eben Emael, Fort Battice and others. OTL Eben-Emael was completed in 1935. I think I had a post starting it back in 1932 or so- a year late if I'm right.
Edit: Thinking about it, that means the Belgians mounted these when the biggest German tank was a Pz-I, the 60mm could likely ventilate that at all ranges.
Belgian fort weapons
I expect I will wind up converting it to a vehicle/towed weapon as Wesworld becomes more cluttered with tanks that belong in the 1940s.