This is a revised edition of "Acorn Box".
In comparison with the initialversion (RF-20-1), the idea is the same. But the way to open the cover is alittle different. When people tried to open this work for the first time,the cover fell onto the floor, because, they didn't know the solution. InRF-20-2, the mechanism has changed, and that won't happen. (For the timebeing, I'll produce RF-20-2 as the standard version.)