The BEP released these notes into circulation in early 1933 to test different percentages of linen and cotton fibers used to see how they would stand up in everday use. The X-B and Y-B blocks had the different ratios of fibers, while the Z-B block (with the standard paper) was used as the control group. Just over 10 million notes were printed in each block making them scarce compared with the large numbers printed of standard issues. This note is in Fine condition. Get it while it lasts!