Not sure about RH, but this is what the debian manpage says:

              A specific version of a package can be selected for
              installation  by following the package name with an
              equals and the version of the  package  to  select.
              This  will  cause  that  version  to be located and
              selected for install. Alternatively a specific dis­
              tribution  can be selected by following the package
              name with a slash and the version of the  distribu­
              tion  or  the  Archive name (stable, frozen, unsta­
              ble).


On Fri, 07 Jun 2002, Amy Tanner wrote:

> Is there a way to use apt-get to install a particular version of a
> package?  I was trying to install kernel-source-2.4.9-31 but the APT
> repository also had 2.4.9-34.  I couldn't find a way to tell it the
> version number I wanted.  It seems, apt will always install the latest
> version by default but surely there must be a way to specify other.
> I couldn't find anything in the man pages on this.  Thanks.
> -- 
> Amy Tanner
> amy at real-time.com