I always wanted to get into correctional currency at some point, and that point has now arrived. I started with the 10 cents: And my most recent addition is the 50 cents. Feel free to post and share your own fractional currency.
Fractionals are on my bucket list but just not right now. Looking at the prices in multiple guides, looks like a type set of the 25 different notes should be obtainable with just a bit of patience -- there's no super-expensive stoppers.
Good luck, I completed a set a couple of years ago. You already have one of the best ones (Lincoln). It's a nice example.
They were issued during the Civil War because there was a severe shortage of coins available in circulation for commerce.