The SATURNO watermark shows the planet with the word "SATURNO" across the top, "JA" (with a scroll below the A) directly below, then well to the left the letter "E" and to the right the letter "B" (both double-line capitals). The "B" and "E" are far enough away from the planet that they are never seen on notes showing any other portions of the watermark.
The ledger lines consist of red vertical (relative to the watermark when it shows) lines spaced at various intervals, the group being flanked by bluish horizontal lines which are 7 .5 mm apart. There seem to be two different layouts of the red lines as shown below:
In Layout 1, the spaces between the red lines are 20 mm. - 35 mm. - 33 mm.
In Layout 2, the spaces between the red lines are 35 mm. and 55 mm.
The horizontal bluish lines extend further than the diagrams indicate (perhaps 7-8 inches) and there are probably additional vertical red lines (single or double) where they terminate.
A note showing the planet watermark in the horizontal position will show all of the red lines described above. In either layout the "JA" portion of the watermark will fall between the lines that are 35 mm. apart.
The layout of the lines on the face of the note will be fairly similar to that on the back.
Notes may be found with the lines running in the directions shown above or the layout rotated 90 degrees or inverted (together with the watermark, if present). The 19 JULIO 1915 U-Series and R-Series notes seem to always have the watermarks and layouts vertical. Thereafter they may be horizontal or vertical, though horizontal seems to be the usual.
The size of the parent sheets of paper and the number of notes that could be derived from them remains uncertain. However, while notes showing portions of the watermark are certainly outnumbered by those which do not, they are not particularly rare. Based on the material studied so far I would guess that twelve notes came from each sheet (3 by 4, with five showing some portion of the watermark) - but that is only a guess.
This paper was only used for 1 peso notes dated 26 Julio, 10 Agosto and 3 Septiembre 1915.