Necro thread but still a relevant topic and worthy of resurrection. (I think there is a similar newer topic in the pool.) I think half cents. All very low mintage, and the values pale in comparison with other low mintage coins, and the survival rates are not very high.
Since this a thread that's come back to life I'll add my two, err, three cents. Based on mintage the three cent nickel is undervalued. The main reason they are mostly affordable is popularity/demand. I find the series fascinating in many ways. The early dates are a clash mark collectors heaven.
It seems that every time I get interested in a coin set, I find that everybody has already collected them and they become hard to find. Like the IHC, my father gave me a bunch of IHCs, so I bought a Whitman and started filling the holes. Then I got to the last hole to fill. With the price of the 1877 IHC being several hundreds of dollars for a "Good" grade, it will be a longshot to find one that I can afford. I was very lucky on one set. My father collected the Eisenhower dollars. He had over 50 coins which was divided between me and my brother. He had no interest in collecting, but didn't want to give or sell them to me. There were several duplicates in my half. I was lucky that he had no idea that it was better to have different year coins, so, I traded my duplicates for some of his coins that I didn't have. I hope he doesn't read CT. I build models also. He told me I could have his whole collection of coins if I would build a 1968 Oldsmobile 442. I just got the model from ebay. Now, coin collecting will be on the back burner until I send the completed model to him. He will turn 70 this year, so I am hoping he is a man of honor. He'll probably claim he doesn't remember the arrangement because of Alzheimer's. Oh well!
Not too long ago, most collectors hated and/or ignored clad Ikes. I have fond memories of those coins when I was a boy. For some reason (I would guess as an "investment"), the owner of a Carpet company my mother was the bookkeepper for bought several large bags of the Ike coins, and kept them in a vault along with the cash receivables through the late 80's into the mid 90's. When I would visit my mother at work, or stay home from school sick, he would give me one of the coins. In fact, this may be my origin story of how I got into coins at a very early age, but I honestly don't remember exactly how, so I can't say for sure. They were big and cool looking to a kid who was around 7 years old. As an adult collector getting back into the hobby I decided they were ugly. Big modern ugly crap. Then at some point, after being in the hobby again for a few years, I suddenly changed my mind again. I am fairly certain it was due to my CAC Type set, and the sudden and unexpected decision of CAC accepting Ikes around 2012. I bought a few, submitted them, and was going to keep one in my set. Well, low-and-behold, holding them in my hands again, they looked big and cool to me. I've thought long and hard about what it is that made me so dislike the coins, and in the end, I think its because they photograph poorly, the design just looks big and ugly and simplistic, and when I would view them online, I had a negative reaction. It probably was a bit of snobbery too. But in hand, these coins were attractive and brought back the fond memories. Well, with CAC accepting the coins, others started taking notice. And while I am sure they are still a pariah coin for a lot of people, if you look at the pricing for high grade clad examples, it's doubtful people would say they are still undervalued. I am posting this as an example of what can happen to undervalued and underappreciated series. They can suddenly become cool again due to things like Registry sets, CAC inclusion, and evolving collector sentiments. Maybe some of the other examples in this thread will likewise experience a boost out of the bargain bins.
After studying mintages every year with my youth coin club, we have all decided that the Barber series is very undervalued especially the Barber Halves. Mintages are low with many being melted. They should be valued higher than the Walkers, etc.