After much Googling, I found how to tell what version of Subversion created the repository that you are looking at. There is a file inside the repository called “format.” Here’s a screenshot of it looks like:

You’ll need to open that file with your favorite text editor. It will contain a number. Here is the meaning of that number:

SUBVERSION VERSION NUMBER           SCHEMA VERSION
-------------------------           --------------
Up to and including 0.27            1
0.28 - 0.33.1                       2
0.34 - 1.3                          3
(no released version used this)     4
1.4 - 1.6.9                         5

Look at the schema version column, and match that number to what is in your file.