Somewhere along the way BL / Triumph changed the material used to manufacture the Radiator Cowls. The later ones we supply are made from a similar material to the Glove Boxes, and are as fitted to the MK4 and 1500 Spitfires up to FM95,000.
If you would like the earlier smooth type these can be found in the MK1-MK3 Spitfire Catalog.