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Casting date from a 1977 Bora ... my guess is that each large dot represents a month and perhaps the smaller dots represents the week within that month. Looks like this wheel was made in March or April of 1978.

The glass also has a manufacturing date. The letter "D" represents the month (April) while the "8" represents the last digit of the year (1978).

There are many other components that have a date code, for example tires are stamped with the week of manufacture (1 - 52), followed by the last digit of the year. This can be found following the DOT numbers.