The 1620 used binary-coded-decimal as you mention, not the 1401’s bi-quinary, so it’s not “the same scheme”, although it did also calculate on one decimal digit at a time.

Leibniz pointed out in 1703 that to do simple arithmetic in binary, such as addition and multiplication, you don’t need to memorize such rules as 5 + 4 = 9, or 6 × 7 = 42. Instead, you need ...

Leibniz pointed out in 1703 that to do simple arithmetic in binary, such as addition and multiplication, you don’t need to memorize such rules as 5 + 4 = 9, or 6 × 7 = 42.