Instruction: Extract the value of the target attribute from the given product information and output it along with the corresponding source.

Input:
Product title: 2008 S US Mint Quarters Silver Proof Set OGP
Product feature: 2008-S US Mint Quarters Silver Proof Set, Complete Original US Mint packaging including Certificate of Authenticity, Contains 5 coins in stunning proof condition, displayed in one protected lense, Quarters are struck in 90% silver, This "vintage" Proof Set has been previously owned
Product price: $28.80
Target attributes: Mint Mark
Answer: attribute: mint mark
value: None
source: None