Some interesting observations, especially the progression/evolution of the ssTek tools:
 - v12: the sole use of (the original?) WPI - "Windows Post Install"
 - v13: still WPI but the introduction of faders
 - v14: the introduction of SetupS and a proto "Setup Silent" WPI but without faders and not very "silent" LOL
 - v15: ??
 - v16: ??
 - v17: a fully refined ssWPI including faders also ppApps make an appearance (though not sure if these weren't introduced in v15 or v16)
 - Apparently v18 and v19 were skipped
 - v20: introduced themes and widescreen and ppGames (though none included)
 - v20-v22: seems to me the same basic "build" but with updates...? Maybe I'll refer to them collectively as v2x ;)
 - v22 (USB): a patched v22 to allow installing from USB hardware as well. 
 - v22 (SOX): the only one to include some ppGames (freeware). It's also the very last LastXP release.