Beim M60A1 bin ich mir nicht ganz sicher, der Lauf und die Einfassung am Turm passen irgendwie nicht so 100%. Hier zum Vergleich noch mal, ab 0:19 sieht man sie ganz gut:

Underwater military museum - YouTube

Boah nice, ich hatte die ganze Zeit schon überlegt, woher ich die Form kenne, aber bin nicht drauf gekommen... =)

Hab's bei Reddit, Insta und Getty Images gefunden. Scheint echt zu sein. Socotra Island im Indischen Ozean. Gehört politisch zum Jemen. Abgefahrene Bilder hier: Socotra Stock-Fotos und Bilder - Getty Images

Tippe mal auf durchschlagene Schiffspanzerung aus dem 2. WK, vermutlich japanische.

Kaputti hat recht, Internet sagt folgendes:

I used to work at the Washington Navy Yard, which is where this photo was taken. It's part of the Washington Navy Yard Museum, which is a real hidden gem in case you're ever in the area.

This plate was originally found at the Kure Naval Arsenal, which is one of the locations where the Yamato class was built. Following the war, the United States used the plate for testing, to see if American 16" super-heavy shells could penetrate it. The test was performed under almost ideal circumstances (as others have pointed out), but it also did confirm that the U.S. 16" shell was an incredibly effective projectile, and very nearly the equal of the Yamato 18" guns.

And for anyone complaining that the test was performed under ideal circumstances, unfortunately that's about the only way that something like this could even be done. There really isn't a good way to simulate all of the variables of combat engagements, much less the boundary conditions (i.e., the surrounding structure that would have supported it) that would have had a significant impact on whether or not the projectile actually penetrated this armor in a battle. The analysts theorized that a U.S. Navy super-heavy 16" projectile would penetrate 26" armor at a 90-degree angle of impact, and the test showed that the analysts were indeed correct.

26 Inch thick armor from Japanese Yamato class battleship, pierced by a US Navy 16 inch gun : WoWs_Legends

Hab sowas selber auch schon im Militärhistorischen Museum in Dresden gesehen, nur waren es da Panzergeschosse auf größere Platten.

Ohne sie gesehen zu haben? - ALLES!

Ein Modell des analogen Taschenrechners "Kalkometer" aus den 30ern:

Kalkometer - circa 1930's Calculator - YouTube