In doing research I was finding a common problem with the sources found on the internet: was it the Anzio Express (Leopold) or Anzio Annie (Robert) that the 168th Infantry Regiment of the 34th Division captured on June 7, 1944? Was "Leopold" named the "Anzio Express" or "Anzio Annie"?

From page 205 of They Fought at Anzio by John S. D. Eisenhower:

The troops and sailors tended to lump all enemy guns under the nickname of "Anzio Annie" or the "Anzio Express." However, the incoming artillery shells were of all calibers. And even "Anzio Annie" and the "anzio Express," the names the troops used interchangeably, were two guns, not just one. One, which the Germans called "Leopold," was located southeast of Rome near the Ciampino Airfield. The other, which they called "Robert," was situated several miles to the south of Ciampino at Frattocchio Station [This coming from - Fatal Decision: Anzio and the Battle for Rome by Carlo D'Este].

From page 261 of The Rock Of Anzio by Flint Whitlock:

The two biggest guns were a pair of huge, 280mm guns mounted on railroad carriages and hidden in tunnels in the Alban Hills. The Germans had named one of the guns "Leopold" and the other "Robert," but the GIs on the beachhead simply referred to them as "Anzio Annie" and the "Anzio Express," the latter because the sound of the shells flying overhead caused some soldiers to imagine a runaway train roaring through the sky.

Direct descendants of the 240mm railroad guns the Germans had used with such devastating effect on the western front in World War I, these two Krupp-made monsters could hurl shells packed with 550 pounds of high explosive up to thirty-eight miles. It took the German crew six to ten hours to haul the guns out of their hiding places - one was in a tunnel near Castel Gandolfo, the Pope's summer residence - and prepare them for firing. As soon as a few shells were fired, the guns were returned to their tunnels.

 

Where are they now?

From S, Berliner III's website:

Here is the "official" 05 Jun 01 Ordnance Museum (APG) version of the story (virtually verbatim):

There were two guns that made up the German K-5 RR battery that shelled the Anzio Beachhead. "Robert" and "Leopold" were the names the Germans gave the two guns. Together, they composed "Anzio Annie." When the Allies broke out of the Anzio Beachhead, the guns were moved to Civitavecchia, located just north of Rome. There "Robert" and "Leopold" were spiked with explosives and blown in place. On 07 Jun 1944, the 168th Infantry Regiment of the 34th Division captured the guns. Leopold was the less damaged piece and was moved to Naples and embarked aboard the liberty ship Robert R. Livingston and shipped to APG. The fate of "Robert" is somewhat hazy; the best guess is that it was scrapped in Italy after the war {if anyone has better information, please supply it, with provenance}. In February of 1946, two more K-5 RR guns were brought to APG from Germany. Parts off those two guns were put on Leopold and the gun was tested at APG.

In 1950, however, those two K-5s, along with a 600mm Mortar called "Karl", a 420mm "Big Bertha", and a 21cm Czech gun, were scrapped before the Museum Director, Colonel {G. Burling} Jarrett could rescue them.

End of narrative. Read it and weep! (My sincere appreciation to APG for this narrative.)

The good Dr. Robinson confirms that "both Leopold and its partner Robert were captured in late 1944" and adds that "a crew member, Albert Saurerbier, destroyed the elevating generator and breech with explosives. It is presumed Robert was disabled as well. However Robert (perhaps another) seems to have seen action later (with Margaret) in W. Italy." Dr. R.'s ref.: "Anzio Annie - She was No Lady", pub.by R. J. O'Rourke.

 

Overview of the Anzio Beachhead

Lurking in the back of this Italian railyard is the massive German railway gun nicknamed the "Anzio Express". This collossal artillery piece, with its sister "Anzio Annie", bombarded the Anzio beachhead from positons high above and behind the front lines. The gun is seen here at Ciuitauecchia, where it was abandoned by the Germans and captured by invading forces.

Anzio Annie