Correction: Mac OSX unzips the file as a .cpgz, not .cfg
4.83 mb seems extremely small for a LR catalog
What you don't make clear is whether or not this backup was on the external HD that had problems, or not? And where is the active catalog file? Do you have that?
If you can't open the backup catalog, then it is likely corrupted and not usable.
On your MAC, see CPGZ File (What It Is & How To Open One)
How did you RECOVER these backups for your catalog. Did you use a recovery program or were they from a backup drive? If you used a recovery program there is no guarantee that it has the correct data it the file. You SHOULD NOT keep backups on the same drive as your other files.
See if this may help.
The file was recovered using an application so it's very well possible that it is incomplete. As for the location of the original catalog file, I am not sure where that is. What naming format would the actual catalogue be in, foo.lrcat, or would it be in some other naming convention? I did some (key word: some) searching at 6 AM before a work meeting for the original catalog and didn't see anything, but I can check again later.
I am well aware that backups should not be stored in the same location, but this was a result of attempting to transfer between machines. Of course, while I'm in the process of system wiping the old machine and transferring to my new main machine, an MBP, I lose everything. 'Tis quite the situation, and I'm not too happy about it.
Well, it looks like my catalog may be toast, but I was able to recover most of my recent RAW files, so not all hope is lost. I may have lost all edits, but perhaps a freshly started catalog will prove beneficial; revisiting pieces could bring some new ideas to light.