1. A METHOD OF SECURING A METAL SKIN IN A MATRIX BLOCK, COMPRISING THE STEPS OF DEPOSITING A METAL SKIN ON AN OBJECT BY ELECTRO-DEPOSITION, PLACING A LAYER OF MATERIAL OF SUFFICIENT THICKNESS OVER THE SURFACE OF THE METAL SKIN REMOTE FROM THE CAVITY OF THE OBJECT, REMOVING SAID OBJECT, ARRANGING THE RESULTANT BODY COMPRISING SAID METAL SKIN AND LAYER OF MATERIAL ON A SUBSTRATUM AND DEPOSITION MOULDING SAID THEREON TO FORM A SAND MOULD, POURING METAL INTO SAID SAND MOULD TO CAST A METAL BLOCK, REMOVING SAID METAL BLOCK FROM SAID SAND MOULD, SAID METAL BLOCK HAVING A CAVITY CORRESPONDING IN SIZE TO THE BODY COMPRISING SAID SKIN AND LAYER OF MATERIAL, REMOVING SAID LAYER OF MATERIAL FROM SAID BODY AND PLACING SAID BODY IN THE CAVITY OF SAID METAL BLOCK, AND FILLING THE SPACE BETWEEN SAID SKIN AND SAID METAL BLOCK WITH A MATERIAL WHICH JOINS SAID SKIN AND SAID METAL BLOCK.