The gasket comprises a peripheral loop of sheet metal encased in an elastomeric material, the core being locally thickened, preferably in the vicinity of fixing screws by lateral projections(14) from the stamping which are folded over to double the thickness, and the double thickness is then joggled to distribute the thicker portions (10) symmetrically of the single sheet portion (12), the thickened portion (10) then being coined to control the dimensions more accurately and tend to lock the edges together. <IMAGE>
