Purchasing coins mostly made of silver?

Well if I was able to purchase them based on face value, for example if old nickels were made of mostly silver… would I then be able to sell them based on their weight in silver? Would this be a good investment?

Is it better to buy silver made in different years?

I want to buy some silver round. They came in different years at different prices. How do I make it a better investment? Buy them made in a certain year or different years? Thank you for any suggestion.