the revision number and a tag

[Michael Hüttermann]

Hello,
given a Subversion tag, what's the best way to get the revision number 
of that tag, i.e. the revision number with which the tag was created? Is 
it possible at all having checked out the tag to a local working copy? 
Or is there any other way to cross-reference a "tag" to a revision 
number?


Thanks.


Michael