I am in my 50's. I have had many different collections through the years, but coins have been the most persistent. My mother collected, and passed along her interest to me. Her father (my grandfather) was an avid collector, including coins.
I collect old US coins, state coins, and foreign coins. I enjoy the process of finding them in every day use as opposed to buying collectible coins. I was given a proof set of state coins (the first five) but I have collected the rest mysetf as I encountered them. I have all of them, but I am always looking for any that are in better shape than my current ones.
I have only found one (a dollar bill), so far, but any "error" currency is also worth collecting.
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-Author prefers to be anonymous.