LM399H Precision 6.95V Voltage Reference. Used.
"Buy It Now" for $6 (plus $2.50 postage).
The picture shows some of the units date back to 1986!
Digi-Key has them, new, for $7.94 each.
Good catch with the date code.
My first though was that for trying to sell precision units, wow, they look like junk and the vendor throws them together in a heap to make them look even worse. The whole point with a precision reference is that you know it will be right when it comes from the factory, the manufacturer is putting their reputation on it. How could you with these? This is the worst auction of a high end component I have ever seen. And yeah, the price is not good considering what these look like. I've dealt with some really good Chinese suppliers but this is off-putting.