And for your amusement:

Few persons, except professional writers, have the least idea of the value of words and the effect that they produce, and the thoughtless letters of emotional women and underbred men add sensation to news items in the press almost daily.

Of course the best advice to a young girl who is impelled to write letters to men, can be put in one word, don't!

I think Reverend would be the proper title; Father is an informal title used in conversation, right?

And I love old etiquette books. My mother gave me her copy of the 1968 Seventeen book of Etiquette. Love it!

OK, seriously, I'm in love with Emily Post:

Never sprinkle French, Italian, or any other foreign words through a letter written in English. You do not give an impression of cultivation, but of ignorance of your own language... For the best selection of words to use, study the King James version of the Bible.

"Reverend" isn't actually a title, though; it's a description. It should be "The Reverend TITLE LAST NAME." That's why I'm confused.

Here's a WikiHow for addressing Catholic clergy.

""Reverend", while not originally a title, has become a title with usage and has been common in the U.S.A. for at least 40 years. It is only necessary to say the last name once, if at all, depending on the circumstances. After that, simply call him "Father". In writing a letter, address the letter to "The Reverend Full Name" and append any doctoral degree (like Ph.D. or D.D.) if the priest has such a degree. Do not address letters to priests as "Reverend Father". In the address field write "The Reverend Full Name, Doctoral Degrees only," if any. Begin your letter with "Dear Reverend Last Name" or "Reverend Last Name" for a greater degree of formality; or "Dear Father Last Name" or "Dear Father First Name" if the letter is informal."

A name tag might be considered an informal situation - most priests I know prefer to be called "Father SoandSo", and that's what a name tag is, right?

Heh. One of the other religious dudes has the last name "Bishop." That must get confusing.

So it's looking like "Father X" or "Fr. X" on the nametag makes the most sense?

I believe Father is the proper title for a Catholic or Anglican priest. This guy says that for written address, you should name him as Rev. Fr. X, but he also thinks the post-Vatican II church is vulgar and crass. Wikipedia agrees, but the matter seems to be of formal letters versus personal introduction. Personally, I would go for Father X on the nametag, as that is how others would refer to him in conversation if they were introducing him. The real purpose of the nametag is to provide a sort of introduction, but if you're still unsure I would ask the assistant what Father X would prefer.

The way I've understood it agrees with what muddgirl and kyleg wrote, so I'd go with Father X.

I'd ask. I've known some priests who, despite being officially Rev, hated it and preferred Fr. because they found the honerific too formal and elevating (these were franciscians, though, who take the humble thing seriously) And some who did prefer the more formal title. (but were never offended if someone called them Father)

Of course the best advice to a young girl who is impelled to write letters to men, can be put in one word, don't!

That's because [sob] WE CAN'T READ!

/oscar moment

*applauds jonmc

Given that his assistant used "Fr. X" repeatedly in her email to us, that's looking like what he prefers. So we will indeed go with that.

Thanks, all.