There are two top tier grading companies that are widely accepted in the precious metals industry as being the two leading grading companies; Numismatic Guaranty Corporation (NGC) and Professional Coin Grading Services (PCGS). We would recommend members to choose coins graded by these companies. Coins graded by these companies generally trade to a premium over coins graded by other less popular grading companies.
For anyone with an interest in Sovereigns, I highly recommend getting hold of the auction catalogues for the Bentley Collection.
As well as a sales tool, it has absolutely invaluable information and very clear photographs of some remarkable sovereigns.
I purchased mine from eBay for £20 which I consider an absolute bargain.