There are eight of the M65 atomic cannons left, which were based to a degree on the 28cm K5(e). I believe one is at Aberdeen and another, which I have seen, is at the Atomic Energy Museum in Albuquerque New Mexico. The others are at the Yuma Proving Ground in Arizona, Fort Sill, Oklahoma, Watervliet Arsenal New York, Rock Island Arsenal Illinois, Junction City Kansas, and Virginia War Museum at Newport News VA.
Their shoulders held the sky suspended;
They stood and Earth's foundations stay;
What God abandoned these defended;
And saved the sum of things for pay.