I'd use "an" if you use the 11/10 form, and "a" if you use "November 10" though I can't say why that looks best to me.

I have the same inclination, but it seems so subjective (depending on how you read the "11/10" part). I figured that since it's grammar it cannot be subjective and there has to be a right way.

As always, when in doubt, rewrite:

"The statement of 11/10" or "The statement dated..."

A lot of (English) grammar comes down to style choice. It isn't always finding the right formula and plugging it in.

Assuming you don't have a style guide to follow, I would go with "an 11/10" statement.

Joan Arkham has it. It's not great spoken form to speak numbers aloud in that construction - "eleven ten," - because it's ambiguous. But you should write as it would sound when you were speaking. Since no one is going to pronounce "11" as "November" rather than "eleven," the article should agree with the word readers will hear in their heads.

But I also agree with Eideteker that you can always rewrite your way out of such puzzles. In this case - why not "a November 10 statement?" Just by spelling out the month, you'll be free of this problem.

In my newspaper career, requirements for spelling out months, days, etc, rather than writing them in numeric shorthand, was specified in the style guides anyway.

I don't have any style guide to follow - it's just an internal email. Everyone refers to the statements in the MM/YY format, so I'm sticking with that format to be consistent. I agree that the article should match how I read it in my head - so an 11/10 statement it is. Thanks, guys!