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

UK, 1804: Platinum Before Wollaston's Sale

On October 5, 1804, a large shipment of 32 chests (~4,000 Troy Ounces; 124.4 kgs) of platina was seized by British Commodore Moore from the Spanish Frigate Médée (Bustamante Guerra) and presumably sold on the UK market (at Plymouth, around October 19th?)  Wollaston's purchase record does not show he acquired this platina in 1805 or 1806.

This bulk platina seizure is 2/3rds Wollaston's 'monopolist purchase' in 1800 and ten times greater than the widely-publicized large bulk sale in New York in 1802. Similar bulk auctions  may have periodically discounted bulk platina in the UK; it is also not known whether merchant banks held platina as a commodity or for what duration.

This Continental/ Atlantic news was reported in London October 25th 1804 and in Haiti March 14th, 1805; there was a 4.5 month lag-time in trans-Atlantic commercial news during the winter months.

 

The Diary of William Allen recorded the early manufactures of Thomas Cock, in late 1804.
(See A history of platinum and its allied metals; Donald McDonald and Leslie B. Hunt, 1982, p139.)  Cock's refined Platinum was not pure, however.

It appear that the amounts indicated were ounces avoirdupois ("56 ounces" = 3.5 lb avd.); "Small Platina" refers to reduced sponge.

51 Troy Ounces platina > 30.9 Troy Ounces Refined Platinum = 65.81% purity

1804/5: 1 Troy Oz. Pt Sponge (33.4833 ozt  @ £ 30.20) =  £ 0.90
1804/5: 1 Troy Oz. Pt, refined (44.9833 ozt  @ £ 27.61) =  £ 0.6138

 33.4833 ozt + 11.5 ozt = 44.98 ozt.

1804/5: 1 Troy Ounce platina (ore; whols.) = £ 0.2468 (USD$ 1.12)
1804/5: 1 Troy Oz. Platinum (intrinsic) = £ 0.3751 (USD$ 1.71)
1804/5: 1 Troy Oz. Platinum (refining cost) = £ 0.4452 (USD$ 2.) 
1804/5: 1 Troy Oz. Platinum (producer price) = £ 0.82 (USD$ 3.71)
1804/5: 1 Troy Oz. Platinum (mfg, retail) = £ 1.659 (USD$ 7.50)


The 1830 British Platinum Low gave pause for reflection; ~27 years earlier,Wollaston's Platinum was not yet sold in London.  Paris-imported Platinum, presuambly Jeanetty's, was 3-4 x higher (at least 35% higher than the Paris Price, to include merchant profit, importer's markup, plus any tariffs.)

1830: 1 Troy Ounce Platinum (Ru ingot) = £ 0.75 (USD$ )
c.1803: 1 Troy Ounce Platinum (ingot) = £ 2.44 - 3.00 (USD$ 10. -13.75) 

c.1798 - 1803:

Factoring the intrinsic rate cited in New York in 1802, early imported French Platinum-ware was likely sold at the Price of Fine Gold.

c.1804 (see 1839)

Gold's Specific Gravity is 19.32-19.33; Platinum is 21.45
Where Hammered Gold is 19.3617; Hammered Platinum should be 21.53

Refined, rolled & hammered Platinum was assumed to have an incorrect specific gravity of "22.07" : probably, ~12% Iridium