USA/UK: Platinum Foil

1808: 1 Troy Ounce Platinum (thin foil in slips, cost)  = £ 0.40 (USD$ 1.85)

1838:

1838: 1 Troy Ounce of Platinum (whols., foil, var.) = £ 0.40 (USD$ 1.85)

1838:
Citation: Chemical recreations: a compendium of experimental chemistry;  John Joseph Griffin (1838)

 



1855:

1855: 1 Troy Ounce of Gold (whols., foil, var.) = $ 32.
1855: 1 Troy Ounce of Platinum (whols., foil, var.) = $ 12.

1855:
Citation: Descriptive catalogue of chemical apparatus, chemicals and pure reagents (1855 Chilton , pp.)

1866:
In 1866 & 1877, Griffin's retail Platinum price was nominally the same, although unit prices varied.

1866: medium Platinum foil, 1" sq., cost £ 0.05 (-25% less than the 1877 Price) @ £ 1.65/oz. (the same nominal rate), the  

1866:

Capsule: approx. volume 1.5 drams, ~135 grains.
Foil cover: 1.5" sq. in. ~ 22 grains ; Foil: 1." sq. in. ~ 14.5 grains.

1872:

1877:

In Griffin's 1877 Catalogue, thin Platinum foil 1" sq. cost £ 0.025  and medium foil 1" sq. cost £ 0.067, both @ £ 1.65/oz.   

Per 1 troy ounce there were presumably 66 sq. in (132 sq.in. of surface) thin foil, or 24.75  sq. in (49.50 sq.in. of surface) medium foil.

c.1876/7: 1 Troy Oz. Platinum (semi-mfg., whols.)  = £ 1.65 (USD$ 8.94) 

Citation: Chemical handicraft: A classified and descriptive catalogue of chemical ... By John Joseph Griffin (1877) p.367

1877:

 
c.1878: 1 Troy Oz. Platinum (semi-mfg., retail)  = £ 1.60 (USD$ 7.82)

1"x1" = £ 0.01125 (USD$ 0.055) presumably Extra-Thin (142 sq. in. per oz. troy) and perhaps wholesale?

Citation: The British Journal of Photography,  (1879) , pp.136

1890: 1 Troy Ounce of Platinum (Market Peak) = $ 20.

1891: 1 Troy Ounce of Platinum (whols., refined, market) = $ 9.

c. 1891/2: 1 Troy Ounce of Platinum (whols., foil, var.) = $14.0 - 18.66

1892: 1 Troy Oz. Platinum (whols., foil)  = £ 1.60 (USD$ 7.79)

1"x1" (Extra Thin) = $0.20 @ $0.60/gr < 0.33gr

1"x1" (Thin) = $0.25 @ $0.50/gr < 0.5gr

1"x1" (Medium) = $0.30 @ $0.45/gr = 0.75gr
1"x1" (Heavy) = $0.40 @ $0.45/gr = 0.9gr

1"x0.5" (2 Medium) = 1"x1" = $0.60 @ $0.45/gr = 1.3gr

c. 1891/2: