I've watched Candleshoe many, many times and one question remains; did Harry Bundage inform Casey of the loose brick in the fireplace, behind which the silver music box lay hidden for several years?
If so, why did Harry's thieving cousin, the ex-housemaid of Candleshoe, not steal the silver box, if (?) she had stumbled upon it previously whilst 'dusting' (Priory and the Lady of the house clearly knew nothing of its existence)?
The playing of 'Greensleeves' at the start of Casey's briefing leads us to believe the housemaid may have known about the music box, but did she know about the hidey-hole in the fireplace?