There was a book I owned as a child in the the early/mid 90’s.  It was a hidden objects, interactive book, where I believe each page represented a different country.  There was definitely something about hidden treasures.  I believe after you finished the book, there were extra challenges at the end.  One of them was to find a particular man on each page.  I can’t remember if he was a good or bad guy (i.e. a detective or a thief.)  The one thing I remember absolutely is that on each page there was a capital letter hidden somewhere on the page.  After you found all the letters, you had to unscramble them and it would tell you the location of some hidden treasure ( I think it was some type of goblet.)  I remember that Brazil and China were two of the countries- I believe Russia was there too.  I think the answer to the riddle was that the treasure was hidden in Brazil.   It was a large hard-covered book and title completely escapes me. It might have been Treasure Hunt or something like that.  Any help would be greatly appreciated.