It's an unusual situation, but not that unusual given that the same thing has happened previously for other prefixes. Notes tend to get printed in batches, and the first prefix in a batch is the one that gets issued last. So we look at the data in the SNDB and we see that prefixes up to HBW are reported in many thousands, then HBY to HCF are reported in lower numbers (couple of thousand per prefix), and then for HCG onward, only a few hundred notes per prefix are reported, except for HCG which is sitting at 7. Because all 7 HCG notes reported have high serial numbers, it's tempting to speculate that something odd is happening, but it's clear that HCH-HCM are not fully issued. We have to remember that these polymer notes have longer circulation lives, so stockpiles or new notes are going to be sitting around that much longer. I have two of the 7 HCG notes, and they are close in serial numbers (both start with 9953xxx). They are circulated. I got them a few days apart, so I thought maybe this meant more were coming, but it has been weeks and I have not found any more.