ok i got an answer from them and this what they told me:"The items that you have look authentic to me.They will probably date from 1920 to 1952 as it as it has an Ede & Ravenscroft label (not Ede & son) and it is to appointment to the King and Queen which would be either George V and Mary(1910-1936) or George VI and Elizabeth(1936-1952)"
than i asked how much they think it worth,and the answer was:"It is difficult to place a value on this items, especially without being able to see them and their condition. If you were to buy them brand new, the wig would retail at GBP 560.00, the gown at GBP 199.00 and the case at GBP 235.00."