USA, 1861

1860: 1 Troy Ounce Platinum (Mfg: Crucible) = USD $ 14.40
1860: 1 Troy Oz. Platinum (Semi-Mfg: Foil) = USD $ 12.00
1860: 1 Troy Oz. Platinum (Semi-Mfg: Wire) = USD $ 12.00  
1860: 1 Troy Oz. Platinum (Sponge, Trade) = USD$ 10.

1860: 1 Troy Oz. Platinum (Scrap, Mkt) ~ USD$ 7.25 - 7.66
1860: 1 Troy Oz. Platinum (Mkt) = USD$ 8.

Where Chas. T. Chester sold platinized Silver sheet per Ounce @ $8.00, 1 dozen No. 8 cost $6.80 or $ 0.567 per sheet, or $ 0.2159/per Sq. In.

A No. 8 Gauge Pure Platina Platinized Sheet 2.625 Sq. In. weighed 34 Grains Troy, just 12.95 Grains per Sq. In. (or, 16.935 cm² weighed 2.203 Grams, just 130 Mg per Sq. cm.) 

Hypothetically, a No. 6 Gauge Pure Platina Platinized Sheet (@15 dwt. per dozen) 2.625 Sq. In. weighed 30 Grains Troy, just 11.43 Grains per Sq. In. (or, 16.935 cm² weighed 1.944 Grams, just 114.7869 Mg per Sq. cm.) 

Citation:  Catalogue of Telegraph Material, manufactured by Charles T. & J. N. Chester, 104 Centre Street, New-York. With Appendix. Chester (C. T. and J. N.), Firm. (1861)

No. 56. – Grove Platina Plates: 3.5 in. long, 0.75 in wide (2.625 Sq. In. or 5.25 Sq. In. Surface); rolled to any required gauge or number. No. 8 gives 17 dwt to one dozen pieces; No. 9 gives 18 dwt.; and No. 10 gives 19.5 dwt, etc. No. 6 is as thin as it is ever advisable to roll platina; it is used from No. 6 to No. 30.

No. 56 per Ounce .................................. $8.00

No. 56a Platina Gauge #8 ...................... $1.25
No. 56b Grove Battery Complete ........... $2.50



Where 879 Pounds Avd. is understood to be 12,818.75 Ozt,
 
1861/2: 1 Ozt. Platinum (Plate: Whols., Import.) = $ 5.2797




Where 11 Pounds Avd. is understood to be 160 Ozt,
 
1862: 1 Ozt. Platinum (Plate: Whols., Import.) = $ 5.2488 
 
Where 897 Pounds Avd. is understood to be 13,081 Ozt,
 
1862: 1 Ozt. Platinum (Plate: Whols., Import.) = $ 5.2818