#USBitcoinReserves The rarity of two Bitcoin blocks sharing the same nonce is due to the way mining works. The nonce is a number that miners repeatedly try to find a valid hash and “unlock” a block.

A nonce, which is an “unsigned” 32-bit value (it can only represent positive values ​​or zero), there are 2^32 possible combinations, which equates to roughly 4.29 billion different values ​​that can be used in that field.

Considering that miners typically scan these values ​​systematically or randomly, the coincidence of a valid nonce in two different blocks is a statistically unlikely, though not impossible, event.