UK, 1856: Newman's Catalogue

Platinum plates of indeterminate thickness were employed; presumably ~2.0 Troy Ounces in total.

1857: 1 Troy Ounce Platinum (semi-mfg) = £ 1.50 - 1.60 (USD$ 7.34 - 7.82) 
1856: 1 Troy Ounce Platinum (semi-mfg) = £ 1.60 (USD$ 7.86)

Assuming Grove's Sheet Battery, ea.: Pt 9.41 Grams/ 145.2 Grains Troy = £ 0.55 (USD$ 2.70), nearly the same price as 1853 elsewhere. 

Citation:A Catalogue of Philosophical Instruments Manufactured and Sold by J. Newman, Philosophical Instrument Maker...1856 p.21

Grove's Battery Form, 8" sq. in.  (16" sq. in . surface) in 12-Cells, with 0.67 sq. in. (1.33" sq. in surface) per cell.

 

Spurious Sovereign