My copy of UK2 is 1983 in the copyright, but its a UK copy... Did they release earlier in the uK? .... I don't have a copy of b7, but it was originally published in 1979, republished in 1984. C3 was 1984 according to my copy, and I don't have O2, wiki says 1984, though that again is a UK release date
The Sentinel has a registered publication date of 1984-02-01 in the US Copyright Office database, but says "Copyright 1983" inside the adventure. Either TSR was tardy with the copyright registration process, or
The Sentinel was delayed slightly during production/printing. I don't think the UK series was released early in the UK -- I have a vague recollection of the opposite, that they were available in the UK slightly later than in the US [citation needed!].
I can't find a registration for
The Lost Island of Castanamir in the US Copyright Office database, but it does have a 1984 copyright date printed inside. It would also make sense for it to have been a 1984 release to have come out ahead of the next title in the C series (
To Find a King, February 1985). But over the years, TSR's production schedule strayed from a sequential release for more than one of their series (the A and OA series spring to mind). I believe that
Castanamir was an example of this, and I think that it only came out in about March 1985, after C4. My main reason for thinking that is an advertorial on page 32 of Dragon #93 (January 1985), which lists Castanamir under "Coming Attractions".
O2:
Blade of Vengeance says 1984 inside, but has a publication date of 1985-02-15 in the copyright database. It's also listed under "Coming Attractions" on page 64 of Dragon #94 (February 1985), which makes me lean towards 1985 for that one.
Rahasia was first published in May 1979 by Daystar West, then republished as RPGA1:
Rahasia in April 1983 and then finally combined with RPGA2:
Black Opal Eye to make B7:
Rahasia. B7 has a 1984-07-30 publication date listed in the copyright database, so it was probably an August 1984 release.