In DAM in TYPO3 4.5 there was a ident field for media. This field is identifier for a object or media in real live.
https://en.wikipedia.org/wiki/Identifier
This only works, if you used the extension "dam_falmigration" for migration and the tx_dam is still present
sql::
UPDATE sys_file_metadata,sys_file,tx_dam SET sys_file_metadata.ident=tx_dam.ident WHERE sys_file._migrateddamuid=tx_dam.uid AND sys_file_metadata.file=sys_file.uid
zip this extension:
zip -r ../taywa_filemetadata_ident_0.0.11.zip *