USA 2017 1 Cent Coins [solved]

Here is a question for our American friends. I have got quite a good collection of USA Pennies.
As you all know they are minted in Philadelphia, Denver and San Francisco.

The Denver coins have a "D" mintmark
The San Francisco Coins have a "S" mintmark
The Philadelphia coins have no mintmark all the way up to the 2016 coin

However the coin minted in 2017 has a "P" mintmark, seems like Philadelphia Mint
decided to make a major change to their minted pennies.

Then when the 2018 Philadelphia coin comes out we find it has no mintmark?

Does anyone know why they have done this?

Cheers Mike

I’ve found a 2018 and can confirm that there is no mintmark.

It was only done in 2017 to celebrate the 225th anniversary of the Philadelphia mint.

Thanks Roublizer ... I never knew that. Cheers Mate

Mike

From "Coin World"

"Although the Philadelphia Mint will likely strike billions of 2017-P Lincoln cents for collectors to find in circulation at face value, examples of the first cents in U.S. Mint history to be struck with a P Mint mark are currently generating secondary market premiums.

The 2017-P Lincoln cents struck for circulation as well the special finish cents created for inclusion in the 2017 Uncirculated Mint set are a one-year type. The addition of the P Mint mark is part of the U.S. Mint’s 225th anniversary year celebrating the contributions to the nation’s coinage history by each production facility.

The P Mint mark will not be included in the design for Philadelphia Mint cents struck beginning in 2018."