Victor/Bluebird Record runout groove change in 1940?

[Benz]

Recently, I've noticed that Victor/Bluebird changed their runout grooves in 1940 circa, as you can see on the images down below, the first record is The Lady's In Love With You by Glenn Miller, recorded in 1939, the second one is Slow Freight, also recorded by Miller in 1940.
The first record has one runout groove that actually serves as one, plus another "bonus" one that it's there just as an infinite loop disconnected from the other grooves, the second one, has only one runout groove.
Does anybody here know why this had been done? Is it connect to some random decision made by RCA or to where and when the record was originally cut?

[recordmaker]

The end of record locked groove is obviously essential for any disc record and I am sure most of us have experienced records issued with an open end groove and the opportunity to damage the label and the sound box at the end of a record.

Additional artifacts are almost certainly required by the factory.
I note that since starting to master discs myself I first relied on the single locked groove to center the mold but it much easier to center the mold using a spare locked groove cut at the same time and away from the music or run out groove.
I currently cut both grooves like the first example to make the centering process easier and more accurate.

In the past there were different mechanical and optical centering devices for stampers and a transition from one to another in the factory could have rendered the additional locked groove redundant.

In the mechanical method a pointer with a needle (or a fork for stamper ridges I think) on the end and long lever was run in the locked groove to indicate run out before drilling the center hole and typically the turntable was rotated by hand so it could be pushed in either direction and in that case the run out groove would have caught the tracking stylus and run it into the music ( backwards I assume ) so with the mechanical method a separate locked groove would be very handy.

Current practice (by which I mean 1940s onwards) is almost exclusively optical with a microscope of some kind.

post script
Reading the comments following I can see these are eccentric grooves, only having a portion of the groove in the picture makes that more difficult to spot at first glance, so in this case the reason for 2 grooves is indeed a mystery to me at least I am not sure if this is simply a carry over from the earlier practice, they needed to be cut into the wax on separate off center turntable after cutting the record.

[gramophone-georg]

The original eccentric runouts first appeared in 1923 to activate Victor's new automatic brake. The double eccentric was continued until sometime mid 1940, when it was dropped for the single groove type. Since these eccentrics were necessary to "trip" early Victor changers, and almost all changers produced after 1936, they probably felt the double groove was necessary for some reason.

Interestingly enough, it appears that in Europe the double groove was dropped around 1931, when records went to a lead- in plus eccentric, e.g., the eccentric placement became standardized.

Why they continued the double groove on USA Victor recordings nearly a full decade after the Euro sister companies dropped it is anybody's guess. Maybe to get around patents? Who knows.

Another curiosity on USA pressings are late Columbia Viva- Tonal discs made in 1931 that employed a lead- in starting groove for a few months- only to have this feature disappear, then become standardized industry- wide around mid 1936.

Another thing that keeps me awake at night is why Victor discontinued gold print in mid 1941, at about 27500.

[recordmaker]

Gold print. Could have been a style/design thing.
But 1941, makes you question where the supply of specialist inks came from in the late 1930s.


in 1914 the specialist dye and pigment supplies came from Germany and the British pressed Edison BELL Winner record went from full colour labels to monochrome for several years.