Yes, I understand that 2ns is normally available on DS2202 models, but mine started as a DS2072A with 5ns as the fastest timebase. What I meant was that I first tried the 300MHz key, but still had only 5ns TB (no 2ns or 1ns) and no model number change (still claimed DS2072A). When I then tried the 200MHz key it converted to a DS2202A with 2ns TB. I didn't try the 300MHz key again after already converting it to a DS2202A, but maybe I should?
Tirulerbach can probably comment more, but he did say the 300MHz option was absolutely untested...