This unusual item is a book cover in sterling silver featuring the popular "Angels" group design.
It measures approximately 11.7 cm long by 7.2 cm wide.
It has an accompanying photograph which appears to be of the design upon which the embossed silver angels decoration  is based.
The second photo is the back of the first, showing the photograph, as found in a Brisbane estate.
A novelty that a silver collector may like as a conversation piece. I have several items from this estate of which many are quirky.