I've been doing a little research on the square nickel with the train engine. I'll post more as I hear back. Steve
Collect what you like. I do and so do most of the other members on CT. I have a wonderful wooden nickel collection. They are, for the most part, inexpensive and full of history. Great designs are on a lot of them. Wooden Nickels are much better commemoratives than what the mint puts out.
I'm new to this genre of collecting. I collect Lions Club pins, ran across a few woods from Lions and started accumulating them. Like anything that you collect, you can be specific or wide ranging as you like. Each tells a story.