Here are two CD 154 insulators from Spain. This picture illustrates mold differences. Both have the same embossing( E.S.A. on the front and C.T.N.E. on the rear) but the aqua piece is much cleaner and refined while the green aqua one is crude. I do not have an explanation for this, maybe production standards got better as more of these insulators were made or maybe some plants produced better insulators than others.