Please work on better focus on your large images, that first one is, well, just terrible.
but all
Lincoln Cent coins of that era were all 'Brass' coins. Brass is an alloy of copper and Tin/Zinc.
In 1941 the Planchets were supposed to contain 95% copper and 5% Tin or Zinc.
if they got the measurements a bit wrong and added more tin than needed you get a more 'Brassy' appearance to the coin.
Quote:
Brass is a metal alloy made from copper and zinc, with the proportions of each metal varying to create different types of brass:
Basic brass: Typically 67% copper and 33% zinc
85/15: 85% copper and 15% zinc
70/30: 70% copper and 30% zinc
60/40: 60% copper and 40% zinc
Brass can also contain other elements, such as lead, tin, aluminum, or manganese. Lead is sometimes added to improve machinability.
The percentage of zinc in brass affects its color and mechanical properties:
Color: More zinc gives a duller yellow tone, while less zinc gives a reddish hue.
Strength: More zinc makes brass stronger and easier to work with.
Brass is known for its many desirable properties, including:
Corrosion resistance: Brass is highly resistant to corrosion
Machinability: Brass is easy to machine and form into different designs
Conductivity: Brass is a good conductor
Low magnetic permeability: Brass has low magnetic permeability
Biofouling properties: Brass prevents algae and barnacles from growing on it, making it useful in marine industries