Here there is a person that calls them "yellow jackets" here is the thread he had on this: https://www.cointalk.com/threads/19...oln-cent-brass-plated-planchet-strike.250542/ Food for thought, hope it helps!
Definition: brassy plated cents are the product of a zinc contamination within the copper plating bath. The presence of the zinc produces a plating that has a slightly yellowish appearance compared with the normal copper with a red, orange or pinkish appearance. The zinc contamination comes from trapped zinc planchets that are retained and ultimately dissolved in the plating bath. They are often found on 1983 and 1998 Lincoln cents, but could hypothetically be found on any year plated planchets were used. curtesy http://www.error-ref.com/brassy-plating/
