Both I's are to a gap.
It's interesting you say that Pete, as all the references to the hollow neck variety, pre Gouby, are of the I of IMP to a border tooth, not the I of BRITT. The earliest reference I can find is Court in September 1972, but no doubt it was discovered prior to that. Gouby doesn't even mention the type in his 1986 book, which covers pennies from 1860 to 1970. But he now says the I of BRITT pointing to a tooth is the determining factor. Although both I's point to a tooth on the variety, so the net effect is the same either way. .
Freeman just refers to hollow necks in 1911 and 1912. I've never seen one from 1912. Peck makes no reference.