By the way, the "crosshairs" mark is the NATO Design Mark. It means the cartridge will fit into any NATO weapon of that calibre, nothing more. It does not mean that it is perfectly interchangeable in all NATO weapons. The NATO Interchangeability Mark is a four-leaf clover without a stem and is only on the external packageing material. That usually means on the wooden or cardboard box the metal cans come in. Small arms ammunition is tested periodically (usually at about 10 year intervals) to see if it still meets the chambre pressure and MV requirements for NATO intercangeability. If a sample fails to meets standards, the interchangeability mark is removed from the packaging.
Also, the date stamp (66, 86 or 77) is just the last two digits of the year the casings were made. The cartridges can be assembled any time after that. The actual date of completed manufacture is marked on the packages (boxes or cans) as part of the Lot number.