Mea Culpa the inners made from pieces of "Dexion" and the outer from thin galvonised[sic] steel sheet, pop riveted together.
Generic: Industrial steel [punched] angle.
Brand/Manufacturer: Link51/Moresecure, Lion Steel, Metalrax, etc. I believe Dexion Ltd (now in administrative receivership) with Dexion Holdings Ltd (Dissolved) once made this too. Some other companies with the Dexion name also appeared to slide into the abyss around the same time.
Mea Culpa: an acknowledgment of your error or guilt. "My own fault"