I did something similar, in that I looked for a collector of chocolate wrappers (an example Kit Kat and Cadbury Fruit and Nut)

I found such collections for sale and checked the "ingredient" lists against the lists of those I buy today. The 'new' poisonous versions have added a number of chemical poisons and lecithin (soya).

I just wish I could remember where I parked my time machine so as to return....