It would be lovely to have such a thread but it is just so difficult to get pictures of bars from the 50s, 60s and 70s. Amazingly, companies do not seem to have an archive department that includes pictures of old bars.
The social significance of product packaging was not recognised, it seems, until Robert Opie started his collection, I think in the early 60s. He has made a lucrative living from producing fridge magnets, postcards, posters and books containing images of products of yesteryear, including chocolate and sweets. You can see some of those products in his 50s, 60s and 70s scrapbooks.