The main burner fuel vaporizer is where fuel is vaporized in only one long tube about 6 feet long above the burner's fire. At where the tube exits the burner pan, the fuel has different branches that it takes to the two jets located at the opennings of the venturi (mixing) tubes. It is this fork in the fuel's path where the fuel is diverted to two different ways that is called the burner forks. aka branch forks.
Dear Rolly, From my original Stanley literature, the Stanley season catalog of 1917 still only shows the bent vaporizing tubes holding the main fuel jets. The Stanley model 735 instruction book dated August 20, 1920 finally shows the branch forks as we know them today. It is my educated guess that the new model 735 of 1918 was the first time that the branch forks were now as we know them. They were finally permanetly attached to the main fuel vaporizer with main vaporizer clean out screws at the ends of each straight leg. From the model 740 Stanley instruction manual, in May 1922 with the introduction of the model 740, the branch forks now had on it a header nut with a screen behind it. Behind that for the first time, where the fuel enters the main fuel vaporizer, is a wire cable about four feet long located with in the main fuel vaporizer.