I know, I have too much time on my hands, but this is how I interprit how rares drop and which ones do:

First, every enemy and box contains a possiblity of dropping a common item or a rare. Which one drops what?

Well, when an enemy or box gets destroyed, a random generator scrolls through a list which contains a set. Those sets include: nothing, common item, and rare item.

Common items have about a 50/50 chance, while rare items have a relatively low chance.

Now, if the generator selects a rare, it then goes into a sub-list of which rares to choose from. It seems that common rares such as scapedoll boards, vestaline, and kubara wood drop an awfully lot, which mean that there are more of those common rares to select from than the actual rares.

Then comes the grandaddy of all rares; Boss Box drops. These are in a sub-list in the rares. If the generator selects a rare and selects the Boss Box rare list, it will select a rare in that list, which is very very rare.

Then you have special drops, which will always drop from a special variation of an enemy and not a hidden monster like the rappies or jaggos. The special monsters include Grinna Beat S, Lutus Jigga, Orgdus, and the Derebelans.

So what do you guys think?