mom and her gold collections

My grand mom is a coin collector. She has coins which are decades old. Even her arrhae and cord that she used when she wed my grandfather are made of decade old rare gold coins. I asked her why she still collects those kinds of coins, she cannot use them anymore. Well she told me that they are said to be good investments, because old coins were said to have gold and silver contents and their value is not depreciating, they are appreciating. But she told me that when buying gold coin one should be very careful. She buys only from known legitimate and sure sellers like United States Gold Bureau rare coins to make sure that she is investing in the authenticate coins. Being a collector she already got an eye in looking for authenticate and rare coins. She told me that she is having these coins not only to satisfy her collection but also she is looking at the economic point of view of having them. At my age she advised me to try collecting such coins rather than the things that I collect. I guess she is right, maybe when I have something to spare, I would resort in buying some old coins. I just have to learn some tricks from my granny.