Gents Flush Fire Alarm Call Point (Break Glass)

Good condition flush call point . I can remember these in my school and i would at a rough guess date it between 1955 to 1965 .Due to the technology at the time it’s un monitored and only makes contact when the glass is broken and the button moves out making the circuit. The alarm panels at the time basically had a bank of relays and low voltage lamps connected to back up rechargeable lead acid batteries. The relays for each zone then connected the bells. 
I have even seen small installations with no relays and the call point was basically connected straight to the bells through the battery. All wiring for this type of point would be installed in 3/4 inch metal conduit hidden in the fabric of the building. This version had a test button that was normally held in place by the metal rim. Preforming a dual function . When the front was taken off ,it stoped the alarm bell ringing until tested . Andy