The numbers are a date code: The first set of numbers stands for the year and day that the piece was made. The second set of numbers is the time stamp that the plotter drawing was completed. This code tells us that this piece was drawn and completed at 4:36.03pm on Thursday, September 19th, 1974.

The numbers are a date code: The first set of numbers stands for the year and day that the piece was made. The second set of numbers is the time stamp that the plotter drawing was completed. This code tells us that this piece was drawn and completed at 4:05.57pm on Thursday, September 19th, 1974.

The numbers are a date code: The first set of numbers stands for the year and day that the piece was made. The second set of numbers is the time stamp that the plotter drawing was completed. This code tells us that this piece was drawn and completed at 3:18.31pm on Thursday, September 19th, 1974.

The numbers are a date code: The first set of numbers stands for the year and day that the piece was made. The second set of numbers is the time stamp that the plotter drawing was completed. This code tells us that this piece was drawn and completed at 10:57.03am on Thursday, September 19th, 1974.