The Junior has wicket globe wires, plain tubes, O-Ring pull and outside lift from 1900 until around 1904-1905 when the globe wires change to Full Wave cross wires, also a rare lantern. The FW wires continue through the 1913-1915 version which has cruciform clasps on the FW wire intersections. In 1916 the change is made to the intertwined wires we see thereafter. So dating the early Juniors is a matter of 4 versions of globe wires and 4 versions of small fill. The 1900-1905 fill has a short neck, slants in the plane of the fount dome, and has the 19th century simple cap. Then in 1904-1905 the fill neck gets longer, still slants and has the heavier diagonally knurled cap. Some time between 1905 and 1909 the fill becomes taller and upright until late 1914 when they change to the stamped fill and stamped cap with large vertical knurling. The three types of caps all have different thread pitch, so they are not interchangeable. The stamped small fill lasts until 1916 when the large fill is adopted. The Dietz logo on the lid and the signature Bulb ring pull start in 1909-1910. I believe all the 3H lantern tubes were changed to 3H,1V in 1915. This may never be verifiable for the Juniors which were, apparently, all made in Syracuse; but, I have verified it on the Blizzard, Wizard, and D-Lite. The Junior has the WAGL bail until around 1934 when it changes to the Lazy S bail and the full corner lift plate.
The Hindi-Devnagiri script was added in 1911 on the front and the back of the Junior fount and this continued into the 1940's. One variation in this was in 1913 when the Hindi was on the back only. The bead in the fount skirt disappears in late 1914.
The production of side-safety lamps would have started at the time of tail light safety laws. For the Junior Side Lamp, that appears to be no earlier than 1909. The Junior Side Lamp changes into the Junior Wagon Lamp in 1914, adding the spring clip, changing the Radical Offset bail to the Lazy S, and the fill to stamped/wrought construction. The Junior Side/Wagon Lamp/Wagon Lantern has Hindi front and back from 1911 until the mid 1940's. In the late 1930's the red lens is larger and no words or logo are stamped into the reflector plate. The Lazy S bail gets a pivot added in the 1940's.
Because all wagon lamps (except the Beacon Dash) were finished black enamel at the factory, stripping the paint on one often reveals bright tin.