Chipicao

I know it's been said before that the only available information is in the first post, and there's no way to find out more other than to remove the heatsinks. But I'm curious to know what the second decimal represents. The first decimal I assume is the IC size, 1 for 256Mx8, 2 for 512Mx8 and only one decimal for 128Mx8. But what about the second decimal? There's got to be a reason for it and somebody surely knows it.