Miniature "à transformations", Anglo-Dutch school of the 17th centuryPresumed portrait of Charles I King of England (1600 - 1649), bust to the left, large collar of white lace , yellow ochre costume , red ribbon. Very rare copy, gouache and gold probably on vellum, with four mica painted in gouache, in an octagonal tortoiseshell case . Size : 5 ,5 x 4,5 cm The miniatures "with transformations", with painted mica allowing to disguise the portraits, were fashionable in the European Courts from the 17th to the 18th centuries. The few examples kept in museums are generally from the second half of the seventeenth century, of a fairly standard oval format and painted in oil on copper. This one, which is smaller, differs in shape, support and case: it is octagonal, probably painted on vellum, and the miniature appears under a rock crystal on the lid (and not inside) of a case medallion that discreetly encloses the mica. The latter is made of tortoiseshell, while most of the known examples are made of boiled cardboard covered with leather and cloth. We are in the presence of one of the first examples of this entertainment, whose politically very marked beginnings coincided with the reign of Charles I, King of England, Scotland and Ireland from 1625 to his execution in 1649. Although there is a lack of studies on the distribution and use of these miniatures, their invention suggests an intention to politically harm the monarch, who could be disguised and thus mocked discreetly and with impunity. Among the four painted micas, the one in red costume makes it possible to transform him into a pope . Other copies presented his wife Henriette Marie de France, more or less recognizable or caricatured (one in the British royal collections). Afterwards, different princesses were represented, disguised in various amusing modes and the game apparently lost the politic