Well, in that case they should be prosecuted for falsification of history.
Indeed, in the 1950s the pre-WW2 fortifications were enhanced by digging in Firefly tanks. These were gutted Fireflies, but still fitted with tracks, pushed into a hole in the ground and covered up with sand/soil up to the top of the hull. They differed from the well-known IJssellinie pillboxes, as those were empty hulls cast into concrete, with their main guns stripped and machine guns fitted in the turrets.
Somewhere in the late 1950s/early 1960s there was a fatal training incident. A 17-pdr round went off before the breech had fully closed. It turned out the ammunition was no longer reliable and this incident meant the end of the 17-pounder gun in the Netherlands Army.
In the 1970s the Fireflies were removed from their positions at Kornwerderzand, luckily one was preserved by the Army.
Some 15(?) years ago the museum was looking for a Firefly to dug in again, they could not find one so they scrounged a 105-mm howitzer turret and put it on a slab of concrete. A totally incorrect exhibit in my eyes, as we can see it confuses the public, and then some. One time a volunteer at the museum told me it was "an orginal 17-pounder atomic gun" . . .
HTH,
Hanno
PS: Rippo, thanks for the pics!