Greg Kennelly wrote:

Typically, how far in advance of the cover date did the railways supply data to the ORER publisher in the era when the ORER was issued quarterly?

Typically about a month in advance, but by the 1950s the validity date often coincided with the cover date. The date of validity of the info in each entry is shown at the very end of the entry, in small italics in the bottom right corner of the last line.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
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Publishers of books on railroad history