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 2013, and is not far beyond the next required overhaul date.
This is being sold for ground use only, and therefore any work to make serviceable is at your own risk.