I took over my Dad's coin collection recently and he has quite a few coins marked "woody". What is it and what happened in the minting process that created it? Thanks in advance.
When you see what looks to be wood grain in the medal. Its is caused by improper mixture of the alloys. You'll see this on cents ,and nickels mostly.
It has to do with the metal used for the coins not being mixed enough. It leaves different colored streaks and can be yellowish or other shades of brown on cents.
because I'm here... It's an improper alloying of the metals. metals are melted and combined to make an alloy. In the case of a lincoln cent, like the earlier years it was to be 95% Copper, 5% Tin and Zinc, this makes "bronze", however, if the alloy isn't fully melted and mixed properly, you can get pure copper streaks, if the tin doesn't mix in well you might get streaks of Brass in the bronze, or if the zinc doesn't mix in well to the alloy you might get phosphor bronze streaks in the finish sheet. All of this is going to look the same when brand new metal, and as freshly minted coin, it will be close to alloyed properly and be a coppery cent color, but as the metal tones with time, the different metal compositions, the slight variation in the alloy not being mixed well enough, it tones at different rates making the streaks stand out.
Here is a definition. https://www.error-ref.com/improper-alloy-mix/ You can do a search for woody threads to.
The key seems to be that in principle, improperly annealed alloys will tone differently, and at different rates than metal with roller lines on it which is often confused with annealing problems. Here is a Japanese 1000 Yen which shows how the toning is affected by the streaks in the metal
When I was 16, it meant something entirely different. How times changes words..... I can tell you it had to do with a bird character in an old Knock Knock movie, the name of the bird being bastardized, somewhat, as to the meaning of the name of the bird.
I think you've gotten it now. Enjoy your father's collection and don't forget to share his, now yours, goodies. You are very fortunate, thanks for sharing.
Just beware of roller lines. They are often mistaken for a "Woody" because they can look similar. Here's an example of roller lines. The difference is pretty obvious from the examples of true Woody's everyone has shared here once you know what to look for, lol.