No objection, xiphophilos. When I said that the release dates of Victor records "were nearly always on Fridays of the previous month" (not: on the last Friday) of the monthly Victor catalog and the DAHR date, I meant the time when records were actually released weekly, which was definitely true from 1923 on but possibly already earlier in the 1920s.
I'm probably opening a can of worms here, but I am no longer quite as sure that Victor's release date was _always_ or even "nearly always" the last Friday of the previous month, as fixbutte claims above.
The Talking Machine World, May 15, 1917, page 78d features an article that is directly relevant to the question:
"Victor Co. Announces Change in 'Opening Day'"
Monthly List of Records to Be Released on the First of Months Instead of the 28th of the Preceding Month as Formerly – Change Effective with August Supplement."
The article mentions that the 28th had been the "Opening Day" since 1906 (actually 1905, see note below), but transportation difficulties and a vote of the dealers motivated a change in practice:
"The first of the current month (as indicated by the date on the supplement) is, beginning August 1, to be the simultaneous "Opening Day" for new Victor records. When the first of the month falls on a Sunday or a holiday, the preceding day is then to become the simultaneous "opening day.""
Note: The 28th was introduced as "Opening Day" in The Talking Machine World, January 15, 1905, page 3.
Based on this, it seems as if Victor releases came out on the 28th of the previous month only between January 15, 1905 and May 15, 1917.
Starting June 1, 1917, the release date was the 1st of the month.
See here again. We find accurate release dates for most Victor records from Sep 1923 to Dec 1928 in the record bulletins printed in Talking Machine World magazine, which has been uploaded to a large extent to the Internet Archive, although months Jan to Jun 1924 and, sadly, Jan to June 1926 are still missing (Jan 1926, however, is there).
As said before, release dates on DAHR are generally the dates of the monthly Victor catalogs but don't indicate the actual release dates which were nearly always on Fridays of the previous month. DAHR shows these actual release days - different from the catalog dates - only for a brief span from Aug 1923 to Feb 1924 (and for few selected later records, e.g. 20140), always consistent with the TMW dates then.
To make dates here generally more consistent, I have adjusted the dates for periods without accurate information (Mar 1924 to Jun 1924 and Feb to Jun 1926) by antedating the DAHR release months (or monthly catalog dates) for one month.
DAHR lists the release as June 1926. One of my fellow mods changed this to May, which may well be correct, but I wonder on which evidence the change was made.
The small "o" above the Nipper logo on this label stands for an Oakland, CA pressing. The label design without any kind of note left to the spindle hole was used between 1923 and 1926 (cf. Michael W. Sherman, A Collector's Guide to Victor Records, 2nd ed., p. 85).