Dinky Toys Dublo 70 AEC Tanker Shell BP Decal Set.
These are water-slide decals. Clean your model first. Soak the decal in a shallow bowl or saucer until the decal can be separated from the backing paper. If the decals are multiples do one at a time. moisten the location on the model where the decal will be applied. This will help get it on the model and adjust before touching gently with a dry sponge to remove excess water after correct positioning. Leave to dry.