Czech glass - Shapes

The shape of a Czech piece is one of the most trusted and faulty methods for determining who the manufacturer is or when they produced the piece. Because so many companies existed at the time between 1918-1938 we have to be careful in attributions to a particular company; more companies are "unknown" than are "known". Some of the reasons- "theories", to why shapes may match but the pieces were produced by two different companies are as follows:

1. The company may have changed names but kept the production of the item going under a the new name
2. One company copied the shape of a successful piece from a competitor
3. A glass worker migrated to another company taking some molds with him or remembering how to produce the same shape
4. A company experiencing pressure to deliver a job quickly employed a neighboring company to produce items to fulfill their order (using the same specks"
5. A piece sold by a glass distributor was "accidentally" sold to an importer with the wrong producers information because the piece looked the same
6. The piece is for a certain use or time year (atomizers or easter egg lidded pieces) and resembles all pieces made for the same reasons
7. A company sold pieces to a decorator (who also manufactured their own glass) but the decorator sold the piece as their production piece because the shape was so similar... Same decorator, different blanks
8. A collector years ago mistakenly attributed a piece to the wrong company and we are having problems with the attribution years later

I am working on a hierarchy for what is more important in determining the manufacturer of all Czech glass. I will look for input on what is more or less important in determining the producer.... later.

Who made What?

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-please feel free to reply