getting a specific revision from a branch

[nazrat]

hi,
i have a file foo with revisions 1.5.2.1, 1.5.2.2, 1.5.2.3 etc. in a
branch "pre-release"
i checked out this branch with -r pre-release.  this, of course, pulls
out a copy from 'head' of 'pre-release'. i'd like to be able to pull
out a particular such as 1.5.2.2 but if i do cvs co -r 1.5.2.2 foo
this will switch the sticky tag to 1.5.2.2 but the file is from 'head'
from the branch, not the revision 1.5.2.2    how can i checkout/update/
get a file at a particular revision from a branch? thanks.