This statement was in a recent E-Sylum [Italics added]:

These replicas were electrotypes created by a museum employee. Hired in 1859, Robert Cooper Ready (1811-1901), replicated objects - including coins - in the Museum's collections. After first casting these Ready turned to electroforming the coins, because of the sharper detail he could obtain by this process. In his lifetime Ready made over 22,000 of these coins; his sons, Augustus P. and Charles Joseph Ready carried on after him. Each signed their electrotypes, RR by the father R and MB (reversing British Museum initials) by the sons.

Ready's replicas were so exquisite it was hardly possible to distinguish from the originals. (It is rumored that collectors occasionally paid more for his replicas than the originals.) The practice of electrotyping coins was halted and replaced by plaster casting in the 19th century. Using plaster casts was satisfactory for studying the image, but of course, unsatisfactory for studying the metal surface, toning and patina.

Many books, however, were illustrated with photographic plates, composed entirely of plaster casts. Perhaps this should be discussed in a future E-Sylum. But for now we should recognize the Ready family for their outstanding lifetime achievement. Their replicas rest in museums for generations to view, to study, and advance numismatic science.

To read the earlier E-Sylum article, see:
BRITISH MUSEUM EXHIBIT: MONEY AND MEDALS(http://www.coinbooks.org/v21/esylum_v21n08a22.html)

Joe Cribb adds:

Benjamin Alsop writes: