I think and say "ex oh" while I type "X0". "Ex oh" has a better ring to it. Seeing a "zero" and saying "oh" has a long history. Say this phone number to yourself - 6950. Most people tend to say "six, nine, five, oh". In fact, if you call 411 directory assistance and get a number, when the recording reads it off to you, it will state any zero as "oh".

Also, consider terms such as "00 Buck" and "30-06". Those are stated as "Double-oh Buck" and "Thirty-oh Six" or "Double-ought Buck" and Thirty-ought Six" ("ought" is the obsolete past participle of "owe" which is a homonym for "oh" as in "O").

Also, keep in mind that "zero" ends with the sound "oh" so "X0" could properly be written as "X 'o" which of course would be said as "Ex oh".

"She's real fine, my four oh...er...four zero nine..." LOL