I don't know if I ever had a 306 apart. But, maybe in a month or so, I'll be able to get my hands on the one my aunt had. I know just where it is and I should be in the area around the end of January
When I get my hands on it, I'll open it up and have a gander at the gears. The 302 had a planetary gear system that was a little tricky, and the 300 had a multi-gear train.
I can tell you that in the later 38-/48- series, the 300s had aluminum gears and the 400s had brass.
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