UK, 1881

1881: 1 Troy Ounce platina (Est.: SPb mkt, bulk 75%) ~ £ 0.4604 (USD$ 2.24)
1881: 1 Troy Ounce Pt (SPb mkt, .999) = £ 0.6139 (USD$ 2.98)
1881: 1 Troy Oz. platina (Est.: London, bulk 75%) ~ £ 1.02 (USD$ 4.96)
1881: 1 Troy Oz. platina (London: ore@ .999?) ~ £ 1.36 (USD$ 6.58) 

1881: 1 Troy Oz. Platinum (Paris: Ingot, .999) ~ £ 1.60 (USD$ 7.785)

1881/2: 1 Troy Oz. Platinum (UK: Sheet, retail) = £ 2.00 (USD$ 9.72)

1881: 1 Troy Oz. Platinum (USA: Coin, Scrap rate) ~ £ 1.45 (USD$ 7.05)
1881: 1 Troy Oz. Platinum (USA: Semi-Mfg, Retail) = ~ £ 2.468 (USD$ 12.)  
1881: 1 Troy Oz. Platinum (USA: European Mfg., Retail) ~ £ 2.542 (USD$ 12.36)

1881: 1 Troy Oz. platina (London, bulk) ~ £ 1.36 (USD$ 6.58)
 

Citation: The Electrical Engineer, Vol. 15, No. 254, 3/15/1893 p.268

Suspect dated price information.

Citation: Amateur Work, Illustrated, Vol. 2 (1883)
The platinum foil costs about 30s. an ounce, but this quantity is not necessarily expended in one cell.