Library with .fcpbundle and some without that extension.

I'm trading Libraries with a fellow editor and for some reason the libraries he sends to me end up with the .fcpbundle extension at the end.

Mine don't show the extension.

Any ideas on why this would happen?

if you right click the library and click "get info" you should see a check-box called "Hide extension"
If that is checked the extension will be hidden in the finder, presumably this setting is not preserved through whatever transfer method you use.

As long as everything works fine you shouldn't need to worry about it.
Hope this helps,
-Mark

Pure. Genius.