Select the option most resembling your bulb from the drop-down menu to proceed to the next step. Please consult "option descriptions" for detailed info.
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FULL OPTION DESCRIPTIONS / IMAGE GLOSSARY: [Option titles are also linked to proceed to the next step.]
OPTION A: Stem seal is a crudely made glass stem or tubing, hemispherical at the top, out of which two smaller fused glass tubing with the leading-in wires emerge. Used in 1879. 
OPTION B: Stem seal is a clear glass tubing, flat on the top, and consists of two smaller fused glass tubing unpressed around each wire and both emerging from the larger stem tubing. 1879 to 1880 only. [46.1]
OPTION C: Stem seal consists of a clear glass tubing having been flattened or pressed together about the two leading-in wires. Smaller glass tubing around the leading in wires omitted. Used from 1880/1881 until 1888/1889. [46.2a-e / 46.3]
OPTION D: Length of stem seal reduced with shorter platinum lead-in wires. Used from 1889 onward. [46.4]
Feel Lost? Returning to Step 3 and re-starting the option process will often help you correct the misstep.