How to determine frequency of PocketWizard Plus II tranceivers?

Is it safe to assume that if there's an FCC ID on it that it's the US frequency?

Do all US models have the same FCC ID or are some different? I have one that's KDS-PW2-003 and am eyeing another but the seller says the ID of his is KDS-PW2-103. Does that matter?

Both the KDS-PW2-003 and PDS-PW2-103 are US FCC ID numbers. They're just for different versions of the PW Plus II.

If there is a frequency BAND in which the unit operates, the FCC ID will only indicate the band and not the specific frequency. That is likely to be the case, for units which have multiple operating frequencies (like A, B, C...etc) in order to avoid interference with another photographer working at the same location.