This manual does not refer explicitly to any particular distribution of eCos or eCosPro. However, version numbers form part of many file path names. In all of these places the version number will be shown like this: <version>.
If you are using the freely available public distribution of eCos at http://hg-pub.ecoscentric.com/ and have used Mercurial to check eCos out of the repository, the version number will always be current, since that is the name of the directory in the repository. When a stable release is made this directory name is changed, in the release, to the number of the release, for example v3_1_71 or v4_0_3.