LONDON - "Mr. Hopkinson exhibited a grand pianoforte, to which is applied his repetition action recently patented." Crystal Palace, and its contents : being an illustrated cyclopaedia of the great exhibition of the industry of all nations, 1851, p. 202 (archive.org)

LONDON - "500 Hopkinson, J. & J., Fabr., 27, Oxford Street. – Grosses Pianoforte mit Patent." Amtlicher Catalog der Ausstellung der Industrie-Erzeugnisse aller Völker, 1851, p. 67

In der Ausstellung ist dieser Zweig der britischen Kunstindustrie sehr zahlreich und würdig vertreten in einer Menge von Grand, Boudoir-Grand und Cottage-Pianofortes, d. h. von Flügeln, Tafelklavieren und Pianinos.

Eine sehr vollständige Sammlung dieser verschiedenen Instrumente stellen aus J. AND J. HOPKINSON von Regent Street und Conduit Street, LONDON. Wir bilden daraus ab einen wunderschönen Concertflügel, das Gehäuse von polirtem Nussbaum, eingelegt mit Elfenbein, Tulpenbaum und andern kostbaren Hölzern.

Die ganze Ornamentation ist höchst geschmackvoll uns sauber ausgeführt, wie denn überhaupt dieser Flügel schon durch sein Aeusseres sich zur Zierde eines jeden Salons eignen wird. Was seinen Werth als musikalisches Instrument anbelangt, so müssen wir uns hier damit begnügen, hervorzuheben, dass die Manufactur langst wohlrenommirt ist durch die Combination von klarem, vollem und doch delicatem Ton, mit Kraft und Mächtigkeit, und dass sie bisjetzt bei allen Ausstellungen, die sie beschickte, Ehren davongetragen hat." Illustrirter Katalog der Londoner Industrie-Ausstellung von 1862, Volumes 1-2, 1862, p. 174

LONDON - "Nous devons citer encore MM. Hopkinson et MM. Collard et Collard. Toutes ces maisons ont des pianos de qualité supérieure, avec mécaniques à double échappement. Nous avons pu constater que leurs pianos droits sont relativement inférieurs à leurs pianos à queue. Quant à leur fabrication, elle est on ne peut mieux conditionnée." Rapports des délégués facteurs de pianos des délégués facteurs d'orgues-harmoniums et des délégués facteurs d'instruments en cuivre et en bois..., Délégations ouvrières à l'exposition universelle de Londres en 1862, p. 5 (gallica.bnf.fr)

LONDON - "The display of musical instruments on the British side of the building and the second shows a patent concert grand, with all the modern is very complete. Having already referred to these, however, we now merely introduce representations of two fine pianos, manufactured by   Messrs. John and James Hopkinson, of Regent Street.

The first engraving is of a cottage grand, with carvings in the Italian style;  and the second shows a patent concert grand with all improvements. This is inclosed in a case- of admirable workmanship walnut, inlaid with ivory, tulip, box, and king woods, exquisitely carved. But it is not to their cases that pianos owe their chief excellence.

Without tho interior mechanism be of the liret oUfig, all the decoration in the world would render them but boxes of worthless discord. In the pianos of Messrs. Hopkinson — who has not heard them at the Exhibition discoursing "most excellent music," under the guidance of highly-educated fingers ? — the outside ornament forms but the least part of their value.

True, they are fine pieces of furniture; but they possess a far higher value, for they are famous musical instruments. To hear them well played is a treat for a professor, much less a mere musical amateur like the writer. In tone, touch, and all the requisites of first-rate pianos, they are perfect — fitted alike for the concert-room or the cottage parlour — brilliant, full, and at the same time delicate, and calculated in every respect to sustain the high reputation their makers have so long had with the musical world.

The valuable improvements in the manufacture of pianofortes lately introduced have all been taken advantage of by the Messrs. Hopkinson, the resources of whose establishment enable them to compete, not only in excellence, but also in economy of production, with the best makers in the trade.

To go to the Exhibition on a Saturday, and to hear a fantasia on one of these instruments, is a treat indeed; and when we come to consider what a complicated piece of work is the interior of a piano — the strings stretched to a tension equal to a pressure of several tons, and yet one faulty wire putting the whole machine out of order — when we think what ingenious appliances arc necessary before these strings can answer to the light touch of a woman's finger — when we see that all the ends for which such an instrument are fully answered, and we find the English piano a highly-finished and complete box of harmony, our wonder and admiration may well be excited.

To say that these instruments are as perfect as they can be made, is to say all that can be said of any piano yet manufactured: to compare them with the instruments of other eminent makers is simply futile. Among the best there can be no better." Cassell's Illustrated Exhibitor: Containing about Three Hundred, 1862, p. 208-209

LONDON - "3412 Hopkinson, J. & J. 235, Regent-st. — Piano fortes and models." International exhibition, 1862 : Official catalogue of the industrial department, 1862, p. 54

LONDON - "[...] and Mr. Cadby, Mr. Hopkinson, and Messrs. Oetzmann Oetzmann and Plumb various grand and cottage pianos." The Illustrated London News, 14/06/1862, p. 616

LONDON - "To Messrs. Hopkinson (United Kingdom, 8412) the Jury award a Medal for great excellence of tone and invention of a pedal for producing the harmonic octave.
Messrs. Hopkinson  xhibit seven pianos, namely :— 1. A full-sized concert grand, in elegantly inlaid walnut case. The action of this instrument is on a peculiar construction originally patented by this firm in 1850, and since considerably improved; the last patent bcing dated in the present year. The ordinary hopper is dispensed with, and its place supplied by a kind of knee-joint. Messrs. Hopkinson have found this action work well, and it gives a good touch, but it has not yet been adopted by any other makers. Models of the new action are exhibited in its original form, and its various stages of improvement.

2. A similar grand, but in plainer case.
3. A boudoir, or short grand.
4. A rosewood boudoir grand, having a highly novel feature in the shape of a harmonic pedal.

This contrivance is so arranged as to allow a frame to descend over the strings, and to drop a light knife-edge of felt exactly in the middle of their length, by which, when the hammer strikes, the tone of the harmonic octave is produced, instead of the fundamental note of the string. The effect is pleasing, and the arrangement so ingenious as to justify favourable notice; but it is necessarily expensive, and must be of doubtful general utility.

5. An upright in elegantly carved case.
6 and 7. Two upright pianos; one of which is constructed to sell at a moderate price, and the other with a new arrangement of the hammer-shaft, compensating for difference between horizontal and upright pianos." Reports by the Juries on the subjects in the thirty-six classes into which ..., 1862, p. 147

8. One of the first necessities for obtaining an evenly toned piano, seems to be that the frame-work shall be of such construction and strength that the various degrees of the strings tensions shall not unequally affect it. Perhaps the next necessity is that there shall be a firmness at the point whence the vibrating portion of the string starts.

To obtain this, makers fit the brass studs over which the strings pass on to the iron frame-work. This operation requires much care, and makers —particularly German and American makers — are liable to permit the strings to be too closely connected with the unyielding and comparatively non-communicative iron framing.

Hence the tone of the strings becomes hard and metallic. Some may consider such tone a desideratum. In Messrs. Hopkinson's iron bijou grand the higher notes have rather a uality of tone similar to that above referred to Messrs. Hopkinson show other instruments; one, an upright piano, made for tropical climates.

The weight of this instrument is inconvenient, and the price (200 guineas) unnecessarily made high by ornament, which is called the style of Louis XVI. The framework seems well adapted to insure an inappreciable affection by rapid variations of temperature.

The bijou pianoforte, £25, by. Messrs. Hopkinson, is fitted with an unchecked action, and the hammers are apt to rattle. The tone of this instrument is somewhat weak and uneven." Journal of the Royal Society of Arts, 1872, p. 890-891

LONDON - "An upright grand, inlaid with ivory and ornamental wood, exhibited by Messrs. J. Hopkinson, was placed in the Fine Arts Gallery, in virtue of its excellence of design and workmanship." The British Almanac, 1872, p. 124

PARIS - "Hopkinson, J. & J.; Manufacturers of Pianofortes and Inventors ; 235, Regent St., London. Factory, Fitzroy Road, Regent's Park, London.
Iron Concert Grand Pianoforte, in oak case, with patent action.
Iron Drawing-room Grand Pianoforte, in walnut, with patent action.
Iron Boudoir Grand Pianoforte, in ebonised and gilt case, with patent action.
Iron Cottage Pianoforte in ebonised and gilt case. " Official Catalogue of the British Section, Paris Exhibirion, 1878, p. 64

LONDON - "HOPKINSON, J. & J. - Horizontal and Upright [overstrung and vertical] Iron Grand Pianofortes ; Pianofortes for extreme climates; Pianofortes with patent organ-pedal attachment; Patent Organ Pedal ; Models of Actions ; Designs for pianoforte cases." The Musical Standard: A Newspaper for Musicians, Professional and Amateur, 08/08/1885, p. 82