why does this penny have...

[ant]

ACNE! lil raised bumps not contact marks but bumps.

 

[James_OldeTowne]

It's a common problem with the adhesion of the copper layer on the zinc core. Those are tiny air pockets underneath the copper skin.

[bsshog40]

Seen alot of this myself. I think we even had a post on this a while back.

[cpm9ball]

It's a common problem with the adhesion of the copper layer on the zinc core. Those are tiny air pockets underneath the copper skin.

 

James is just being kind. Lincoln had gas.

 

Chris

[BillJones]

It's a problem with the plating process when the copper coat is applied to the zinc. Back when I was in the market for a 1983 reverse doubled die cent, I saw one of those coins where the copper had actually chipped off the surface of rather large bubble. Knowing the chemical reactivity of zinc, I thought to my self that one could easily put this coin in an envelope, become careless about its storage and find that you would have an envelope full of dust in 10 to 20 years’ time.

[richbeat]

This was a common problem up until about 1985 or 1986. After that, there was significant improvement. While you can still find some bubbling on more recent dates, it's nothing like it was back in the early to mid 80's.

[physics-fan3.14]

This was a common problem up until about 1985 or 1986. After that, there was significant improvement. While you can still find some bubbling on more recent dates, it's nothing like it was back in the early to mid 80's.

 

Correct. After the mint switched composition in 1982, they had a heck of a time with the plating process for the first few years.