Alsace - Lorraine War of 1870-71

I always seem to revisit this complex few stamps and years. I was
looking at some stamps for sale, type II, Scott # N8 - N14. Since I've
owned few of these I took out the Serrane Guide and starting reading
about forgeries. I can't measure the stamps' burelage (one of the
tests) since they are scans on the internet BUT I noticed in the
mention of the "Geneva forgeries" that the color frame margins have
gaps where they come together in the corners. All of the stamps that I
see in the sale have 1 to 3 gaps in the corners (little white lines
either horizontal or vertical. Anyone out there have knowledge or
opinion on the margin gap in authentic and forged?
Thanks,
Tom