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It is not known exactly when this modification to the cover plate was introduced, but it seems to have been in the late 1920s or early 1930s, and it might have been Eterna who introduced it.
If you have any knowledge about this, please let me know.
Note that the setting lever screw is an exception to the rule about screw placement, it can be in different places in stem set and pin set varieties of the same movement, or absent altogether if the keyless work is negative set.
The keyless work under the dial that handles stem winding and setting is often said to be the "fingerprint" of a movement.
For example, The Bestfit Book includes the diagram shown here of the parts of the keyless work of ETA calibre 715 and Eterna 710.
The most significant part for identification is the largest part, the cover plate.
This has an integrated detent spring which holds the setting lever in either the winding or setting position.