Woodgrain effect, It's when they don't mix the metals in cents quite right and it leaves it looking like woodgrain.
Sometimes it the metal being of a wrong mix or something like that. It's like a wood grain look refered to as a woody.
it is as everyone else already said a "woody" which is a copper cent where it has an improper alloy mixture. not worth a premium typically these sell for less than a non "woody"
The "wood grain" is a toning effect. It is not seen on a then newly minted coin which were bright evenly colored. Over time, a mismixed area of mainly copper ( tones darker) and copper/zinc ( tones less) produced an effect similar to the grain of wood through exposure to atmospheric or environmental effects ( mainly sulfur compounds). As mixing procedures for the metals improved in latter years, fewer were eventually seen.
