UK, 1816

Wm. Cary sold Dr. Young 32.225 ozt Platinum  for £ 28.20. Cary was retailing Wollaston's (Manufactured?) Platinum for 17.5s/Ozt.
 
1816: 1 Troy Ounce Platinum (Cary: Semi-Mfg, Bulk)  = £ 0.8751 (Fr 21.70)
1816: 1 Troy Oz. Platinum (Ask?: Scrap, Fletcher)  = £ 0.5641 (Fr 14., S$ 3.90)

1820?: 1 Troy Oz. Platinum (Ask?: Scrap, Johnson)  = £ 0.6441 (S$ 4.45)
 
Wollaston's bulk platina purchases are both consistent with these price variations and ~75% - 80% of the wholesale price quoted to chemists.

Wollaston sold ~3,100 Ozt (~96.4 kgs) Platinum in 1816.

Usselman (1978: PMR Vol. 22, No.3) noted that Wollaston's orders typically took 200 days (or nearly 7 months) to deliver, sometimes much longer.   This suggests at least 3.5 months trans-Atlantic delay of news to/from Cartagena (if London<>Kingston was 4 months' round trip) and five months to Choco.  
 
Between the Spanish source and the London market, the forex variation between the Spanish piastre and Pound Sterling (Paper currency) explains how merchant banks came to dominate this trade.  Beyond mere commodity, platina may also have had a role as collateral in Jamaican merchant debt and against all forms of paper (monetary substitute.)

1815: 1 Troy Oz. Platinum (retail)  = £ 1.25 - 1.75 (USD$ 5.89 - 8.25)

Bollman's Presentation to Great Britain:

Dec. 1816:  

London: $S 1. (Paper) = £0.1458 ; $S 6.857 = £ 1.
Jamaica: $S 1. (Spanish Coin & English Paper) = £0.33 ; $S 3. = £ 1.
London: $S 1. (English & Spanish Coin) = £0.2156; $S 4.6377 = £ 1.

Citation: A complete system of theoretical and mercantile arithmetic; George G. Carey (1817) p.357

c.1816