“One person could accomplish it in a matter of a few days travel time once the first copy was completed as a template”
I would suspect that it is microfilm, instead of microfiche, or at least that is what I have found. So you have to replace, or splice (which could be readily detected) an unknown number of reels, doesn’t seem very feasible that this would be done (but it could be readily accomplished as most places I have been, except state archives) are fairly lax.
It was found—according to the person who sent the e-mail to Texas Darli’—on microfiche, the sqaures of film you place between two pieces of glass and slide around under the reader.