Localizers use various translation tools for their needs and suits. Firefox localization requires translations of DTD and PROPERTIES files, where plain text editors are most common in use. Plain text editors can not serve translation tool features like, Translation Memory, Terminology management, accelerator checking or Identical messages to English ones. L10n Dashboard on Mozilla server does provide the number of entries that are Unchanged for each individual locale however the entire list of entries that are not changed is not available anywhere.
CopyNPaste Finder searches for translation messages that are identical to English ones, basically unchanged entries. So, you can translate those messages if they were missed. It does not check for CommandKeys, AccessKeys, or Keys in this search.
Many times it happens that while going through compare-locale results from dashboard, we tend to just copy and paste the English messages that are missing and forget to translate unintentionally. This tools helps us to figure out such untranslated message.
Result is not so accurate as this tool also includes messages that really need to keep as it is, just like English ones. Tool can not identify such messages. However, it would be really easy for Firefox localizers to quickly go through the results and identify the messages that are supposed to be translated.
Check results for your language: Translation CopyNPaste Finder for Firefox
Your feedback to improve the tool would be really helpful!