Which are the top six coin types that are hardest to find in Mint State condition?

I collect BU Red Lincoln cents. These coins should be way down a list for ease of finding MS examples. Since I joined this forum, a Trade dollar expert has gotten me interested in his area of collecting. I bought the Top trade dollar variety book and purchased my first Trade dollar - a frosty white BU but with several chops. That made me think of an interesting question for all the members here, especially the dealers and deep pocket collectors.
WHICH COIN TYPES ARE THE MOST DIFFICULT TO FIND IN MS? Please rank them at least 1 to 5 or more so the result will be more accurate. I cannot join you because I know little about Type coins. From what I see, Trade dollars might just make the bottom of a ten coin ranking. Early copper type should make the list.
1.
2.
3.
4.
5.
I just thought of something to make this question better. TWO LISTS ARE NEEDED.
List 1-5: Indian, Shield, Barber, etc. era...
and
List 1-5: The earlier Type coins.
I hope my question will be worth the time it takes experienced collectors and dealers to answer.
Comments
1808 QE, 1796 No Stars QE. Maybe Chain and Wreath cents but I've seen both every time I've looked. 1796-1797 half dollars.
Otherwise, I'd expect to be able to buy all others at any time. Definitely any type within the budget of close to 99% of the collector base.
A moot question for most collectors, if one is looking at early type, especially if gold is included.
Among the 19th century non-gold coins attainable by most collectors, everything is readily available; however, I’ve found capped bust dimes and quarters are tougher to find in acceptable MS.
If you do have ample resources to complete a type set, just check the pop report to find the most challenging types.
Chain Cents and Classic Cents are both especially tough. If you count beaded border Lib Cap cents they should top the list. There. That’s 3
Empty Nest Collection
Matt’s Mattes
Interesting that the beaded border isn’t included in the large cent type registry set but is included in the full registry type set. I’m omitting it from my list.
Why don't you ask @Married2Coins ?
Early walkers, Standing quarters and all Barber coinage is tough.
Also Buffalo nickels, Liberty head nickels, and anything from the 18th century.
Sometimes, it’s better to be LUCKY than good. 🍀 🍺👍
My Full Walker Registry Set (1916-1947):
https://www.ngccoin.com/registry/competitive-sets/16292/
I assumed that the OP was asking about type coins. Types or series?
Dumb assignment. I’m taking an F; same grade as the poser (of the question).
There are numerous minor types in US collecting that I ignore. This is definitely one.
Draped Bust Small Eagle half dollars.
In honor of the memory of Cpl. Michael E. Thompson
I find this argument compelling except for the fact that I am building a comprehensive one-cent type set 😬
Empty Nest Collection
Matt’s Mattes
Large sized Capped Bust Quarters
Classic Head Large Cents . . . .
Drunner
Connecticut Colonials
Here are some tough ones:
Draped Bust Quarters
No-motto Eagles
Various single year QE types (No stars,1808, 1848 CAL QE)
Small Eagle Half dollar
Classic Head and Chain large cents
Draped Bust dimes
Flowing Hair dollars
But in general, you can find most type coins in the US series in UNC condition if you watch auctions for a year or two.