Any ideas what might cause this?

JRocco

This bubbling on this 99 Lincoln appears to form a crescent like pattern on both the obverse and reverse. Any ideas why this planchet defect would form in this pattern?

Murphy

Is it like what ya see on a lot of 1983 cents? I'm curious to know what causes it too.

Rob790

It's just a poor plate job on the zinc planchet. In 1983 the planchets were solid zinc and they were really bad cause the plate would peel and formed lots of these bubbles. Later they added 2% copper to the zinc alloy to help the copper plate stick better, but you will still get occasional bad plate jobs, probably just dirty zinc planchets prior to plating. The pattern is arbitrary, dirt/gunk can form any pattern, including the ones shown. Could also be a nonuniformity in the zinc planchet where the 2% copper was not uniformly alloyed, but I'd bet on dirty planchets.

NoGvmnt

Are all those 9's filled or is it just the pic?

That type of bubbling is usually cused by a bad plating job and was probably helped by hot dies.

Jim

LincolnCentMan

I've got one like that... I think it's an 88-P. It came from a mint set.

David

Goober

That's ugly, mint should refund double.

JRocco

The 9's are not filled, its just a reflection of the light source in the pic caused by uneven surfaces. The blank was heavily polished on the obverse. It was just weird to see the bubbling form such a distinct pattern, especially on the reverse.

GoYankees

From an older thread...

These bubbles will break in time and since zinc easily oxidizes, the bubbled cent will corrode.