Some comments/suggestions from me...
5 centuries per thread (1499-1000, 999-500, etc). Or maybe the first one is 1599-1100, etc as suggested by @j1m.
1600-1101, you mean; there is no year 0.
I suppose that works; there are very few narrowly dated coins prior to 400 BC (in fact we might want a cut-off partway through
the 4th century BC), and having a thread for 600-101 AD instead of 500-1 AD avoids the mildly problematic situation of a thread where approximately nothing gets posted in its first two months or so (instead the void gets moved later, when some Byzantine/Sassanian cons would already have been posted).
one week per decade, so each thread lasts a year
Catch up is allowed if late by one decade (other ideas?), since the point is to get some coins out here that we haven't seen before, or haven't seen in a while.
My suggestion is that catch-up is allowed within any
point of the thread in cases where someone has a coin with a 1 year (or less) range from a year that hadn't been previously posted as such, to maximize the amount of single years.
Other than that, either one or two decades of catch-up seems reasonable.
we differentiate from the Decade thread by keeping the date range for the coin narrower; up to 3 yrs? (5 yrs?)
The suggestion in the other thread was that we allow any
date range, even if over a decade, but post the coin on the earliest year of said range. This would allow some posting in areas where narrowly dated coins are scarce.
I'm not actually sure which direction is better. There will always be a problem of when to post coins that fall across multiple years and/or multiple decades (especially if the later part is also the larger one).
and we differentiate from both the Decade thread and How Far Back by keeping moving whether we get a contribution or not.