There is no such coin as a 1878 Seated Liberty so it is a fake coin
with no Numismatic value.

Definitely damage, it is only an error if it happens during the striking of the coin
and there is nothing on that dime that could happen at that time.

Not an error, it is the edge of a tellers stamp.
Technically it is damage.

Not sure where you see an error, all I see is damage at 11.00

Welcome to Coins and Canada

First of all, what city or town do you live in.
Also are you able to provide clear photos of the coins if requested.
When you say uncirculated, that could be anywhere from MS60 to MS67

Looks like it may have been buried for a while.

All US coins between 1965-67 had no mint marks so you won’t find one with one.
Where did you get that pricing from?

Do they have lowball sets for currency like they do with coins?
This would be a perfect candidate.

It is one of a series of I believe 6 issued to commemorate the 1980 Olympics.
There were about 4 1/2 million of each produced and are made of cupronickel.
There was also a silver set produced that came in a presentation box.
Yours with the case is probably worth $8-9.00.

There is a complete listing for *CD notes in the Banknote section.

This is a pattern coin.
DC-25 is the number Charlton has assigned to it.
As far as I know, there is no record of any mintage but it would be very low.

Although most people are keeping those, I don’t think that once they have been circulated the value will go up too much over face. You can buy uncirculated ones for 4 dollars. Too many people ( myself included) bought special wrapped rolls from the RCM when they first came out so there are many in M...

Looks like the Repunched A variety to me.
I’m sure if there are any new varieties, they would have been discovered in the last 150 years.
What are you seeing that leads you to believe it is a new variety?

Hard to make an offer without pictures and variety. There are 5 varieties of the 1870 alone.
Also the condition would greatly affect the value. Do you know what grade each coin is?

Welcome to the forum.

That was gold plated by a third party after it left the mint.
To a collector, that would be considered an altered coin.