A Victorian pearl and diamond tortoise brooch

A Victorian pearl and diamond tortoise brooch, modelled with a blister pearl shell, edged with rose-cut diamonds in foiled closed-back settings, and similarly set legs and tail, his head highlighted with old and rose-cut diamonds and circular-cut red stone eyes, gold mounted, (later fittings, one red stone replaced, pearl untested for origin), length 2.4cm
Condition report:
The blister pearl has an uneven, rippled appearance to the nacre, with scuffs, scratches, nicks and pitting to the surface. The blister pearl is untested for origin and the back is concealed by the mount, therefore we are unable to confirm whether it has a mother of pearl/shell backing. One of the diamonds to the feet has a large chip and the remaining diamonds have a typically greyish, fractured appearance, some stones with chips/surface-reaching fractures. One of the red stone eyes appears to be a later replacement and both have surface wear. The mount has general surface wear, scratches and nicks/chips, with patchy thinning to the edges. The fittings are later replaced/added, with dark solder joins at the junctions to the mount. The brooch pin and clasp are currently functioning. Metal standard is untested. Gross weight approx. 3.8gm.