In a previous post here, I noticed that the silver prices between Shanghai and London were decoupling, with premiums as high as 10%. I didn't know where to find this Shanghai Exchange silver price.
But today I think I found the site that gives these gold and silver prices (for free).
You can find it on Bloomberg:
And when Bloomberg restricts access to their site, you can find it here: http://www.sge.sh/publish/sgeen/sge_price/sge_price_daily/9550.htm
Gold for example: On February 1 the Shanghai gold price was: 334.63 RMB/g. Which is 39339 Euro/Kg at 8.506 EUR/CNY. The London price of gold on 1 February 2013 was 39297 Euro/Kg. So the premium was 0.1% (which is normal because there shouldn't be a premium).
Silver for example: On 21 December 2012 the Shanghai silver price was: 6.277 RMB/g. Which is 760.8 Euro/Kg at 8.25 EUR/CNY. The London price of silver on 21 December 2012 was $29.89/ounce or 22.61 euro/ounce at 1.322 EUR/USD. That's 726.9 Euro/Kg or indeed a 5% premium as was reported by Andrew Maguire.
This also means that I'm going to monitor the Shanghai Silver and Gold premiums to London market with this data on a daily basis!