Please can someone explain the "FMB 1.5" re: D875PBZLK

I'm looking at getting this motherboard: intel D875PBZLK FMB 1.5, from what
I understand FMB means it'll take a prescott CPU (not sure if this is
correct). What does the 1.5 refer to, and is there any way I can tell if the
board I'm ordering is a FMB 1.5 version, if the store doesn't state that it
is?

thanks for any info.