.OCS File

File extension ocs seems to be primarily associated with eDoc DigiSign from Fujitsu and used for one of its default file types. Most likely some special designed document format.

MIME: application/x-edocdigisign

How to open:

It is likely that these documents can be opened in the original eDoc DiginSign.

How to convert:

Perhaps some kind of export to other document formats was possible using eDoc DiginSign.