WWII Era 50 cal pen with armor piercing bullet

Some of you will recall my write up on a modified way to make 50 cal pens using 3D printed inserts and ball bullets

Can Anything Defeat a Level IV Plate Body Armor? -The Firearm Blog

Armor Piercing Caliber .30 M 2

50 caliber bullet hi-res stock photography and images - Alamy

50 cal 700gr Armour Piercing saboted round with exposed Tungsten

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50 API Projectiles 100 PROJOS FEDEX ONLY!

Original U.S. WWII Sherman Tank Gun 75mm M72 Armor Piercing Inert

WWII Bullet Pen – History Salvaged

Help with identification please: .50 cal and 25x193R Hotchkiss

How do armor-piercing bullets work? - Quora

BARRETT 50 cal ARMOR PIERCING round testing through steel