First Day Cancel for Date of Rhode Island Tercentenary with Texas Centennial Stamp

Rhode Island Tercentenary Issue First Day Cover
300th Anniversary of the Settlement of Rhode Island
Issued on May 4, 1936 in Providence, RI - Scott #777

Unlisted Cachet Design with First Day Cancel on Date for RI Tercentenary
with Texas Centennial Issue instead of the RI Tercentenary Issue

I suspect that the Cachet Maker sent his covers to the Providence Post Office to receive cancellations for the RI Tercentenary Issue and one of the clerks/postal workers inadvertently placed the Texas 3-cent issue on the cover by mistake. The Texas Centennial stamp was issued just two months earlier on March 2, 1936.