However, a specialist article on the Society web pages - https://www.chinastampsociety.org/files ... -small.pdf - states they the Express Letter stamps were issued in “late 1912.”
From a random assortment of stamps I happened to notice this one: It's the Republic's 1st Express issue (Chan E8) with a clear Shanghai circular date stamp bearing an English date 6 Nov 1912.
Is this the earliest usage?
The stock # on the stamp -'0499' - suggests it may have been second out of the book for use at presumably the main Shanghai P.O. - if they were working from the back of the book. The stamp itself is sound but lightly creased.