It's the Catalan translation from
this thread. It shows the flag of Spain with the language on the ZWC (Admin console doesn't show flags).
The flag of Catalonia isn't included in the Zimbra installation, we tried to put it in but couldn't find a way to do it. We used ImgFlagCA.gif (language code is ca or es_CA, depending on who you ask) and even tried adding it to the flags.gif file, which I later learned is a merge of all the ImgFlag##.gif files.