1957 ushered in a new era for Monopoly. Gone were the multiple editions. There was only one set available, a yellow boxed #9 with beautiful train graphics on it. This game came with a red bound board with a picture of the box top on it. Other than this the components are the same as the last white box. This set was downsized slightly later in the year and renumbered to #12. The #9 retained the size of the old white box #9 (10 3/8 x 20) and the #12 was resized to 10 1/8 x 20.
This was the first #9 to have Monopoly written down the long sides of the box. This box design lasted for only a year.
In 1958 there was a new box design. The new box was still yellow, but revived the graphics from the old white box. The biggest difference was the inclusion of a picture of the board on the left side of the box top. The box was still the smaller size, but was renumbered back to #9. The Monopoly down the long sides was removed again as on the white #9s.
1959 saw the box changed slightly. "PARKER BROTHERS REAL ESTATE TRADING GAME" was added to the left side of the box top above the board, "MARCA REGISTRADA" was moved from above the list of cities to below the word "MONOPOLY", and "MONOPOLY" and graphics are added to the long sides of the box.
In 1960 copyright dates were added to the picture of the board, and the slogan under the word "MONOPOLY" was changed from "PARKER BROTHERS TRADE MARK NAME FOR ITS REAL ESTATE TRADING GAME" to "PARKER BROTHERS TRADE MARK NAME FOR ITS REAL ESTATE TRADING GAME EQUIPMENT".
1961 saw another slight change to the box, Des Moines was added to the list of cities. Other than this, this box is the same as the 1960.
The 1958 to 1961 games all seem to have been available in two versions, one with a black bound board and wooden tokens and one with a green bound board and metal tokens. As these games were made in the days before shrink wrap only the components were sealed inside the box. This meant that some of the boards could have been swapped and these games are known to exist with the tokens and boards mixed and matched.
I have divided these sets into 5 different years. Parker Brothers probably did not change the sets on January 1st of each year, but I have found this is the easiest way of dating these.