I was reading an article recently and the person was describing symptoms their dog was experiencing.

They took the dog to the vet and described the symptoms. We will all recognize these symptoms. He is not acting right. Tired, threw-up once, just seems off. It started about a day or two ago. He was just fine and then acted strange, the next day he seemed fine.

After several trips to the vets and one to the emergency clinic, the owners learned the problem. Earlier in the week piggy banks were empty and some pennies were left on the floor. The young dog knew the pennies were treats.

Pennies minted after 1982 contain zinc. Pennies are too heavy to pass through the stomach and can become lodged in the stomach wall. The copper is dissolved and absorbed. The zinc is slowly absorbed, depending on the dogs size, age, and overall health the condition can linger and become gradually worse.

This link is not to the article that prompted this but the information is the same.
https://www.vrcc.com/safety/pennies-cause-zinc-poisoning-in-dogs/

Dangerous items with Zinc (this list is not complete)

nuts, bolts, hardware, and other galvanized metals
Diaper rash medicine
Coins – Pennies minted after 1982 96%
Zinc Oxide – SunBlock
Staples
Some toys
Denture Creams
Certain lozenge brands
Jewelry
Game pieces
Zippers
Shampoos, Deodorant
Vitamins

Common signs to watch for:

Weakness, Lethargy
Depression
Pale gums (anemia)
Vomiting
Increased breathing
Increased heart rate
Lack of appetite
Diarrhea
Excessive hemoglobin levels in blood and urine
Discolored Urine
Dark stool
Yellowing in whites of eyes – Jaundice
Death