General Observations About The Coils

The watermark on a flat plate coil will be "horizontal" (aligned with the design).

Watermarks on rotary coils are "vertical" (at right angles with the design).

Genuine flat plate pairs almost never have aligned perforations.

Pairs made by Richard Kiusalas (the inventor of the guage) always have aligned perforations and holes that appear to be a bit small, because they are not elongated from the pulling of the sheet through the flat plate perforator.