[poopicus]

High five for using 'PIN numbers' and not caring about repeating the word 'numbers'. That'll probably drive some people nuts, but not me!

[bobbles]

In this case it actually works because he's looking at the 'numbers behind the PINs' :)

[sixothree]

Blame the people who coined the initialism, not the public who uses it the way that sounds best.

[inportb]

I just call them PI /pɪ/ numbers!