This is an emergency oxygen mask for the captain and first officer - normally found in boxes to the side of each seat. The EROS masks are rare and add the final piece of realism to your cockpit - or just an option to protect against Covid-19.(possibly)
This mask includes the two connector leads, oxygen supply and microphone. The unit carries a sticker confirming it was overhauled in 2012, and is just over 2 years beyond the next required overhaul date.
This is being sold for ground use only, and therefore any work to make servicable is at your own risk.