What do you mean it was only used for 6 months if it's about 4 years old?
You can located the date on the same sticker where it say dart right on the plastic housing like for numbers.
No problem on the shipping! But it does matter "WHY"? Recently I purchase a reeflo snapper Gold. The owner located in LI claim the pump was new never used. He stated he purchase 2-3 years for the purpose of a backup. When I received the pump, there was salt crepe and rust. I contact a reeflo have the pump was 6 years old. Before purchasing I should have asked for the manufacturer date to avoid all the stress and lies. When we sell we want to trust each other. You would not want it to happen to you. Good luck selling