An excellent example of such a "clue" is the Jerome Gambit entry from the Oxford Companion to Chess (1984) by David Hooper and Kenneth Whylde
Jerome Gambit in the Italian Opening; an unsound gambit that can lead to much amusement in light hearted play. It first appeared in the American Chess Journal, 1876, recommended by the American player Alonzo Wheeler Jerome (1834-1902) of Paxton, Illinois.While games and references to Alonzo Wheeler Jerome and his gambit can be found in the June, September, November and December 1876 issues of the American Chess Journal, it turns out that analysis appeared two years earlier, in the April 1874 issue of the Dubuque Chess Journal.
Confusing these two journals, by the way, is not difficult. As Tim Harding wrote in his "The Kibitzer" column at ChessCafe.com in 2007
...[T]he Dubuque Chess Journal was started by Professor Brownson in 1870 and he stopped it after number 73 in summer 1876.
He thought he had sold the rights to W. S. Hallock, who produced the first two volumes of The American Chess Journal, beginning with June 1876 and numbered consecutively from Brownson, i.e. he started with number 74... It was published in Hannibal, Missouri, from June 1876 to December 1877...
Hallock apparently did not pay Brownson (or at least that is what Brownson said) so Brownson restarted his magazine as Brownson’s Chess Journal in February 1877, also resuming with number 74. At different times, Brownson varied his titles...
Having re-established his rights, Brownson stopped in 1878, but resumed again many years later... The last three Hallock issues (his incomplete volume 2) were bi-monthly, with the November-December issue very short. Here he announced he had sold his rights to Dr. C. C. Moore in New York...
Because of moving everything to another city, there was a delay and the new series of The American Chess Journal began March 1878... It ended July 1879.
Moore then sold to Barbe, in Chicago, who did his best to continue The American Chess Journal as a quarterly...
Barbe published Vol. 1-Vol. 2, no 3 (Oct 1879-Dec 1881), but actually number 3 was April 1881. To increase the confusion, the issue of October 1880 was headed volume 1 no 5 on the title page, but as this was a quarterly, it should have been vol. 2 no. 1, as Barbe must have realised subsequently. So then comes January 1881, headed Vol. 2 no 2, but the page numbers are continuous from October 1880. Then April 1881 was the last issue...
After the end of Barbe’s series, there were no Journals until Brownson resumed in 1886.Got it, right?
