In trying to assess the value of your jewellery you may find the following of interest.

1 A New Replacement Value of your piece Is the  price you would pay for your item in a retail situation. For example a Retail Jewellery shop situated on a main High St or modern Shopping Mall Consider this 100% 

1 New replacement values are arrived at considering the intrinsic value of a piece workmanship labour costs and added tax (VAT)  and add on the cost of keeping a High St shop fitting it stocking it staffing it and insuring it. So the high Street needs the 100% price to offer their customers choice and service

2 The Sale Between  Parties This value would be placed on a piece should you wish to make a private sale to an individual and would represent Circa  60% of the retail price. Offering the seller a better price and the buyer a better buy. 

3  Sale at Auction This price would normally be between 30% and 40% of the retail value

4 Probate or Executry Value would be the price calculated at date of death and could be 20% or less of the retail value.

4 Selling Your Piece  However when you come to sell your item that is where the difference in values occurs. and the seller should  try to realise this when presenting goods for sale.