I have been to this Museum several times in the last
few years and have seen no such plate indicating that
this flag has anything at all to do with the Warren Rifles.
It is (and has been for many years) clearly labeled "Lee's
Battery".
The flag has the names of several officers of Lee's Battery
written on it!
For the record, a description of the flag of the Warren Rifles
does survive. It was a Virginia State flag and not a ANV BF.

Ken Legendre