After the model by Joseph Pitts (active 1830-1870) British, dated 1949

the base with a printed label to the top inscribed: Copy of Model under the direction of / Admiral Sir William Keller K.C.B. / from the painting by J. SHELL R.A. / in his possession, by / JOSEPH PITTS / LONDON / 1853. / modelled by D.N. CALLAGHAN R.N. / 24th November, 1949 at the R.N.C. / Dartmouth. 

Dreweatt Neate, 7 September 2005, lot 160

Overall, the condition of the brass is good, with minor dirt and wear to the surface consistent with age. There is particular light dirt in the crevices. There is very minor pitting to the surface. There is an old label to the reverse. The condition of the socle is good, with some flaking to the paint.
"In response to your inquiry, we are pleased to provide you with a general report of the condition of the property described above. Since we are not professional conservators or restorers, we urge you to consult with a restorer or conservator of your choice who will be better able to provide a detailed, professional report. Prospective buyers should inspect each lot to satisfy themselves as to condition and must understand that any statement made by Sotheby's is merely a subjective, qualified opinion. Prospective buyers should also refer to any Important Notices regarding this sale, which are printed in the Sale Catalogue.
NOTWITHSTANDING THIS REPORT OR ANY DISCUSSIONS CONCERNING A LOT, ALL LOTS ARE OFFERED AND SOLD AS IS" IN ACCORDANCE WITH THE CONDITIONS OF BUSINESS PRINTED IN THE SALE CATALOGUE."

The present bust was probably cast from scrap (gun) metal by officer trainee D.N. Callaghan at the Royal Navy College in Dartmouth. A common practice after World War II, scrap metal casting accounts for the weight of this bust.