Seeking Grammar Police Ruling - Typo's

[sistermagpie]

> bboyminn:
 
> Just as gov't and int'l for government and international have
> given way to govt and intl as acceptable forms, doesn't mean
> the originals are incorrect. Just because typo has become
> the common form doesn't mean that 'typo.' is wrong. I suspect
> typo' is somewhat correct as it indicates letters have been 
> left out. 

Magpie:
Why typo' instead of typo'r according to your rule with the plural? If 
we're following the example of int'l and gov't?

-m