An Interesting Wells Fargo Cancellation On Scott U59

In a recent post I mentioned that I had put aside a few items for further study. I present the attached one for any comments or observations.
I know the early 1860s was a period of interest in the postal history of California. The Wells Fargo oval cancels are well known in conjunction with the Pony Express. I'm also aware that Wells Fargo relationship to the Postal Service went beyond just the Pony Express as shown by this quote from Scott Trepel's 2005 treatise on the on the Pony Express stamps.
In March 1861 the Overland Mail Company was authorized by Congress to run the Overland Mail route over the Central Route (effective July 1). The contract also included the Pony Express. Effective April 1861, a three-way arrangement between the Overland Mail Company, Central Overland and Wells, Fargo & Company evidently established Wells Fargo as managing agents of the Pony Express, with Central Overland maintaining operations between the terminus points.
Might this oval cancel on Scott U59 bear some relation to the complex postal history of the period? Your comments and observations are welcomed.

U59 was issued in the 1864-65 period (I don't see an earliest known use in the catalog) long after the Pony Express. The transcontinental overland mail did not use a Wells Fargo postmark. Your cut square was probably a WF use within California but there is no way to tell for sure without the entire envelope

U59 was first issued in September of 1864 according to Tiffany, Bogert and Reichert in their catalog dated 1892 and published by the Scott Stamp and Coin Co. of New York. SPQR is correct that without the rest of the envelope we can only speculate without ever being certain.