Just for information: I have a chip with the label "25FS406" (i think it is a Sanyo "LE25FS406"). Flashrom detects the chip as "SST25WF040B".
It seems that this chips have both the same ID's: id1 0x62 id2 0x1613
Chips are a little bit different in Voltage: LE25FS406: 1.65-2.10V SST25WF040B: 1.65-1.95V
But i tested the LE25FS406 and it seems to work (read, erase and write with function 0)