david.bordeaux

Using a bain-marie and a thermometer. The temperature fluctuated between 85 and 95°C.

There is also this one. The reverse is actually quite good.

This experiment was with 5% sesquicarbonate at room temperature for 6 hours. The green spots have gone but the coin looks stripped and cleaned. I'm going to try 2% at room temperature with a shorter contact time.

According to the Proclamation of 30 July 1971, recognition of the silver crown, double florin, florin, shilling and sixpence as currency refers to coins minted after 1870. The florin (1993), shilling (1990) and sixpence (1980) were later demonetised leaving only the crown, double florin and Maundy coins.

Another trial.

Susan Hicks Beach was also the model for the Britannia on the trade dollar. There was an article in Coin News in July 2024. Pages from CN JULY 2024_opt.pdf

The verdigris may not show very well in the photo. Below is another "before" photo under different light. Work is in progress on coins with more obvious/stubborn verdigris. I will report back!

1. I bought mine on Amazon. It is also available on eBay and from pet shops (for use as a buffer in fish tanks). It is sometimes branded as "Borax substitute" or "Crex" but read the label carefully - it must be sesquicarbonate. 2. Yes, Brita filters remove chlorine. 3. Yes, but not so effective as a quick dip in acetone.

I don’t like using proprietary products because I don’t know what’s in them, and I believe VerdiCare is difficult to obtain in the UK anyway. After some research on what the British Museum used to use to treat bronze disease and verdigris on large objects, like cannon, I tried the technique for myself on this battered 1799 half-penny. For anyone interested, the treatment was 100 minutes at 90°C in a 2% w/w solution of sodium sesquicarbonate in chlorine-free water. Followed by a rinse in chlorine-free water to remove the chemical and then a rinse in acetone to remove the water. The heat is needed as the reaction is impossibly slow at room temperature.

For anyone using the Google Drive workaround, don't forget to set the permissions: right click > Share > Share, then change from "Restricted access" to "Anyone with the link" (Viewer).

Also trying a link to Google Drive to see if that works: Obverse link Reverse link

Could anyone kindly help with identifying this penny? HENRICUS [III] on the obverse and I think I can make out a sceptre. With a bit of imagination, the reverse legend might be NICOLE ON LVND. Possibly Class 5, but I can't narrow it down any further. Any help would be much appreciated. Penny_B_O@0.1x.pdf Penny_B_R@0.1x.pdf (Posting PDFs due to the recurring 403 problem.)

If a silver proof does exist, and assuming it is the same thickness as the cupro-nickel crown, it would be more easily identifiable by weight than by the unreliable "ring" test: Cu-Ni: 28.27590 g (the standard weight given in the Coinage Act 1946) .925 silver: 32.82 g .999 silver: 33.16 g Otherwise, a silver coin of the same weight as the cupro-nickel crown would be noticeably thinner (about 2.47 mm compared with 2.91 mm, so easily visible to the naked eye when placed side by side). This is due to the differing densities of the metals/alloys: Ag 10.49 g/cm3, sterling silver 10.3845, cupro-nickel 8.9455.

I spoke to Graham Dyer two weeks ago at the Michael Dolley symposium in London and can confirm that he is still an encyclopaedic source of information on the Mint. Best to contact him via the Mint Museum, as Rob suggests.

The entry for 4337 in the 7th edition of Bull has been corrected to read "Struck in cupro-nickel".