Hello there. You all seem like wise people - I'd be very interested in your thoughts... I am trying to come up with a scoring mechanism - a Magic Number that tells me how good a coin that is, so I can identify the worst coin I have in stock, and make sure I sell that one before a better one. We run a little eBay Shop, and, like most collectors, I imagine, fund purchases for our collection by selling duplicates. It's easy to decide which is the better coin when you're only comparing a few at a time, but when you're trying to choose from hundreds, you need a system. That system has to be able to compare apples with pears, as it were. Is this UNC G-VI halfpenny better or worse than this Fine George V halfcrown? Which would I rather keep? I think I'd keep the UNC, but what if it was a 1925 Halfcrown? Oh, well that might be different - I might keep that and sell the common UNC. Do you see what I mean? What I do at the moment is take the following factors: 1) Grade, converted to a number (I use a home-made 50 point grading system) 2) Rarity Rating (according to ESC or Peck), converted to a number 3) Metal composition combined with weight, so a halfcrown gets more than a sixpence on this measure, for example, and a silver coin always beats Cupro-Nickel, Copper, or Bronze 4) How much we've been able to sell examples of that coin for in the last 12 months, adjusted for grade. (For each coin we sell, I calculate an UNC equivalent figure, i.e. how much we could have got if that coin had been UNC. Then for the coin that's being evaluated, I take that UNC equivalent figure and factor it down from UNC to the grade it's at.) 5) then I bung in a tie-breaker of Age, so two coins that score the same thus far will be separated by 1 point per year of Age difference. Each of these inputs is subject to a fiddle-factor that I change whenever it throws up something I don't like, so I might reduce the importance of grade if it's throwing out low grade Scarce G-V silver and keeping all the 1967 UNCs, for example. This is all great, at the risk of turning Coin Collecting into adventures with Excel, but it has never really settled down - I seem to always be changing the fiddle factors.... How do you good people decide what to sell and what to keep? thanks for listening... Declan & Suze the Pwincess and the Coin Collector