The Panzerjäger Triebwagen 51 history is here

The Panzerjäger Triebwagen 51 was a German armored railcar designed for anti-tank purposes from the end of the second world war. Its history is scarce.
In addition to the classic armored trains (panzerzüge), the German army was equipped with light and heavy railcars. Among these, it was planned at the end of 1944 to build five (51 to 55) with anti-tank vocation (panzerjäger) armed with two turrets of panzer IV ausf H then ausf J. These heavy vehicles apparently never saw the combat. Only three saw their construction started and only one was completed. It was captured by the Americans in the Steyr factories and placed in a depot in Augsburg where it was photographed (the photos we have), two others were damaged by aerial bombardment during their construction in the Linke-Hofmann factory in Breslau.