A first edition of "Trixie Belden and the Mystery of the Emeralds." Books after 13 were first issued in the 'Deluxe' series. This one was not a particular favorite, so I probably only read it about 10 times- as opposed to the hundreds of times I re-read the others.
A first edition of "Trixie Belden and the Mysterious Code." The one I originally read- and still own- was one issued in the '70s, so I've never seen this cover. Another clever idea: Trixie writing s-o-s on the tags using those characters from the St. Nicholas Magazine alphabet. I also loved the whole Valentine's Day dance story, with Trixie having to buy a girdle- an unusually feminine plot line.
A first edition of "Trixie Belden and the Mystery at Bob-White Cave." There was no 'glossy' version of this book; only the first ten were issued in that series. This was the 'cameo' series, which included the first 13 books (the last three of which were first editions). I always felt sorry for the fish and worms caught in the cave, since they were going to be sold for medical experimentation. Even in the 4th grade I objected to vivisection.
A first edition of "Trixie Belden and the Marshland Mystery." It seems an odd choice to pick the scene where Gaye fakes a faint for the cover art. Trixie turns 14 in this one; on May 1st, which makes her a Taurus.