Founded by Charles Diebold in 1859, it first began manufacturing safes and vaults for banks. It later got into armor plates for military tanks, pnuematic tube delivery systems etc. However, in 1970 this company launched a more renowed product, which is commonly used today. What is the product known as?

ATMs (D) is correct. Diebold started making safes in 1859, then diversified into military products and pneumatic tube systems. In the 1970s, they pivoted to what became their core business - automated teller machines (ATMs), becoming a global leader in banking equipment. Photocopiers (A), inkjet cartridges (B), and Post-it Notes (C) were made by Xerox, HP, and 3M respectively.