Probably because of their impending involvement in WWII. They will have needed it '...for the war effort...'
copper shortage during the war. The us was making pennies out of aluminum during that same period. They made pennies out of steele during WWII. These are known as 'Steelies'
The US made pennies of copper (95%) in 1941 and 1942, and partially from old shell casings in 1944 and 1945 (so the copper content may have been slightly lower in those years). Only in 1943 were pennies made of steel (with a zinc coating) in an effort to save copper for use in the war effort. Probably because they needed copper for the world war 2 effort. ww2 the need for wiring in the military Short answer: The US was using all the coper for munitions used for WWII. copper was required for the war effort i.e. to make electrical cables
All British predecimal Pennies from 1860 to 1967 were made from bronze. The percenatge of the metals in the alloy changed a little over the years, but from 1945 to 1967 they were 95.5% copper, 3% tin and 1.5% zinc.
US Coins issued before 1945 were comprised of 90% silver (penny excluded), and have a much higher values than those issued 1945 or after (in general). in 1942-1945, many pennies issued were made of steel (as copper was needed for the war). These war pennies also have a high value due to their rarity.
All U.S. nickels from 1866 to 1941 are made from 75% copper & 25% nickel. From Oct 1942 through 1945 the nickel in the coin was replaced with silver. In the 1946 the composition went back to copper-nickel.
Nobody mints 100% copper pennies. These days, copper is far too expensive to be minting low denomination coins such as a Penny, and many countries that still produce their lowest single unit of currency coins, do so from steel. Even in the old days copper was alloyed with other metals to produce "copper" coins. The closest the Royal Mint ever came to producing a 100% copper coin was in 1944 and 1945 where the copper content got up to 97%. Usually it was 95% copper.
Presuming that you are asking about US Lincoln pennies, the answer is that it depends. If the pennies are pre-1982, they are 95% copper and 5% zinc and weigh 147 to the pound. If the pennies are post-1982, they are 2.5% copper and 97.5% zinc and weigh 181 to the pound. In 1982, both types were made. In 1943, pennies were made from steel coated with zinc (so-called "silver pennies" or "steel pennies") and in 1944 (and I think 1945 as well) from old brass shell casings, so their counts would be a bit different.
The US entered World War 2 in 1941 and the war ended in 1945.
Japan colonized us from 1941 to 1945.
Broadly, 95% copper and 5% zinc. In 1943, they were produced from steel with a thin coating of zinc. In 1944 and 1945, there was a small (about 2%) amount of tin in place of a bit of the zinc.
1939 - 1945. USA fought 1941 - 1945
Henry A. Wallace was Vice President from 1941-1945 under President Franklin D. Roosevelt (1933-1945)