Identify media content template?

I am trying to move the ‘share’ button to the top of a page. The page in question is displayed after the user clicks on a gallery image.

http://tarlatanas.com/?attachment_id=95

I don’t know which php template file controls the display of this page. Can anybody help please?

As a relative novice at wordpress this is a question that has come up several times for me. Is there a definitive way to find out which template has been called for any particular page?

Most grateful for any help!

Thanks

James