Is there an easy was to find the quality setting of an ogg file without saving a copy at different settings until a match is found?
The ogginfo tool (from the vorbis-tools package) tells you this:
Nominal bitrate: 192.000000 kb/s
Upper bitrate not set
Lower bitrate not set
Vorbis stream 1:
Average bitrate: 209.243033 kb/s
So you can infer from this that it's q6, because nominal bitrate is 192, and no upper or lower bitrate bounds were set.
Although I'm not 100% sure if this is completely reliable. It should be reliable if indeed a qN setting was used, but not sure what happens if exotic encoder options are used.
Note that ogginfo is a command-line tool. You have to run it from a console/terminal window (in Windows, that would be a cmd.exe command prompt window.)
I don't know about "quality" but bitrate is kilobits per second. So, as long as you know there are 8-bits in a byte you can calculate the average bitrate from the file size and playing time. (Embedded images can throw-off those calculations. Other metadata & file headers are usually insignificant.)