Dating Corgi Juniors

[MrHorsepower]

As above, does anyone know how to determine the age of Corgi Juniors, or just how to tell whether or not they are pre-1983?

I collect the pre-83 Corgis and I've recently acquired a load of Corgi Juniors. Some of these are obviously pre-83 and some are obviously post-82, but there are some I'm not sure about. Does anyone know of a way to determine the age of these, so I can finish putting the cars on my shelves and get rid of the ones I don't want?

Thanks.