This specimen shows slight doubling of the center, a somewhat common printing variety that could be attributed to at least two printing deviations:
1. Tumbling of the plate causing a shadow image as the center was printed.
2. True double printing when the first center image was deemed to be too light and was overprinted with a second, darker run.
Here are two scans of the watermark.
The second type is a 1L Zarate, the 1L5, which upon close examination looks to be a group of two or more papers of which their study I am postponing for later.
This remarkable specimen has the frame slightly double printed. The two possible reasons listed above apply to this stamp.
Here are the backs showing an almost completely illegible watermark.
