2c Washington Coils Help

Hello friends,

I am a recent joiner. Postal history is more my thing but I have lately returned to stamps, at least in a small way. I'm tempted to lose patience right about with Washington-Franklins (for one thing, I hate the smell of watermark fluid!) ... so, concerning the attached scan of two perf 10 coils, I am curious about the measurements. The one on the left is 18-3/4 mm wide by 22mm high on my rule, and the one on the right is 19-1/2 mm wide by 22-1/2 mm high. I know the cautions about using rules instead of other verified stamps, but even if the absolute measurements are off I presume the measurements of these stamps relative to each other (made under a magnifying lens) are legitimate?

Can I assume that the left one is flat plate and the right one is rotary press? And why is the one on the right distinctly larger in BOTH dimensions?

Thanks for any help. I'll be posting another 2c coil question shortly...

There is a much easier way to determine flat press stamps from rotary ones than measuring. Usually, flat press stamps will have ink spots on the back since the freshly printed sheets are stacked on top of each other before the ink can fully dry.

OTOH, rotary printed stamps will have "clean" backs since th ink does dry before anything else touches it.

Very true, but the question still stands, why does the coil on the right have both a greater width and height than the stamp on the left? I am curious also.