You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "what is the shield on the back of a penny?" whose answer is Union Shield.
Each document should contain about 30 words, and these documents should contain useful information.

Query: current design of the back of a US penny
Useful Output:

Doc 1: The reverse design features a Union shield emblematic of President Lincoln's preservation of the United States.
Doc 2: It's a combo of the mercury dime and walking liberty. The eagle on the reverse is very similar to the walking liberty design except its head is
Doc 3: In 2010, the penny adopted its current design: the Union Shield. This represents Lincoln's preservation of the United States as a single
Doc 4: From US Mint press release: "The current Lincoln cent's reverse (tails side) design is emblematic of President Abraham Lincoln's
Doc 5: The first penny was issued in 1793 and featured the head of an allegorical woman with flowing hair to symbolize liberty. (obverse) and 15 chain