Matchbox Lesney 10 c Sugar Container Truck Tate & Lyle Decal Set.
These have a transparent background the discard sheet may be either light blue or white, it comes off when soaking the 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 in on the model and adjust before touching gently with a dry sponge to remove excess after correct positioning. Leave to dry.