? about ps2 version

[Executioner]

I'm pretty sure I've got a v5 or v6. Here is what I know.

Model # SCPH-30001 R
S/N # FU068****
8 screws on bottom
yes it has the set screw in the expansion bay.

My question is, all of the FAQs I see about finding what version you have say if the s/n is U (whatever) it's a (whatever). I'm thrown off by the F in the start of my s/n. Do I just ignore it? Ultimately, I know I'm going to have to look at the motherboard to be accurate but I confused by the F.

Thanks.