Hoyarex filter holder. Superb system that was overshadowed by Cokin. Filters are 75mm Square. Some were glass. Holder has an option to take a high quality hood. See other listed items for filters adaptors and the hood.
one of spring clips that holds adaptors in has broke. The other two are enough to clasp the ring, so it's still useable. If you want it secure and have one lens you use you could play safe and glue it