I would think this bell is probably from the early 80s . The earlier versions looked almost the same but you had to specify if you wanted it to work on AC or DC . Where this one is universal. Although basically a domestic bell most electricians opted for the Friedland equivalent as it looked better. Having said that ,due to their high reliability they were often used as door bells in commercial premises and also warning bells to indicate a malfunction on machinery. They were often factory fitted on coin operated arcade machines to warn the operator of a coin jammed.giving unwanted free plays . 
Andy