How to determine the year of manufacture of the vial?

Such questions I packed inbox. People send photos, any codes, passwords, secret, encryption, and is required to name the exact year.
Vintage from modern to distinguish possible, if you know the highlights of labeling bottles.
EMB code appeared in the 1979 - 1980-ies, and applied to bar codes. Decrypt it is not, it simply indicates the time period.

Icon e (estimate) appeared on boxes in 1980 - 1981.

In 1990 - 1991 years was introduced barcode.

In 1992 on the boxes and bottles began to print green dot icon.
green dot

If no estimate, no emb, then you have a very old version of the 80 year. For most brands on the old labeling and packaging of information, it is not, and I do not see any reason to calculate the exact Year of vintage spirits. For them, the more significant the storage conditions, and the older spirits, the more this is true. Just relax and enjoy your newfound treasure!
Anything under 1991, ie already with barcode Vintage personally I do not think, but you have every right to think differently. To convert the barcode on the network, there are many quack calculators. You can have fun with them, can be determined by batch code.