Hi Roger,
I just checked this out on my Tuner [which is n the house to aid testing].
It works as PKi described, i.e. ; and . goto 87.5 and nowhere else no matter where you are (AM or FM).

I note that 0-9 in Tuner mode goto Preset N within current preset bank)

Edit: #1 Oh yeah I have a Mark2 running 2.0 Final and Hijack 325

Edit: #2 The . and ; commands in AM mode go to the lowest AM frequency for your location [i.e. 522Khz for "European" (9Khz steps) areas].