This is an authentic Omega cream watch hang tag that came with an Omega Seamaster Steel Chronometer Diver 300m mans 212.30.41.20.01.003 watch. Your tag measures 3cm by 2cm and still has the original string. The writing on the back reads 21230412001003, 86440736, 2500.
21230412001003 is the model number, 86440736 is the serial number and 2500 is the movement number.
These tags are not available for sale individually from Omega and are only ever sold with a watch. This is a rare chance to complete your set so your watch has everything it was originally sold with.
I have given you photos of your watch tag from every angle. Please use them to add to this description.
If you have any questions then please contact me at Sales@TheWatchLink.co.uk. I'm here to help you.