Which seems like the correct article when writing?
A '05' code
An '05' code
I go with the 'an', but maybe that's because I've got some crazy written/audio connection that isn't necessarily universal. Then again, I'm also thinking "oh five" when it could be "zero five". Oh English, you silly bastard child.
- wispering
If "oh five" then "an"
If "zero five" then "a"
I immediately assumed "oh five".
Which is why "an historical" drives me batshit insane every time I see it.