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That is a very common problem. Kids and liquidation of their parent's "treasures". I have made it very clear that my model trains are a big part of their inheritance they should not treat lightly.
I only have two shelves of antique books. Mostly just classics but a few interesting things like an original Boy Scouts of America Handbook - hardback!?!!
At the peak of the Covid-19 work from home with zoom meetings and the like, folks got so desperate for intelligent looking backgrounds they were paying $75 per foot of books to put on the shelves behind them for the camera. Didn't matter what the books were as long as they looked impressive in the background.
have several note books, in case they miss one, with references to certain items and how to get the best price.
one notable item is NEVER sell jewellery gold specifically with gem stones to a jeweller they only pay you gold weight and the gems are disregarded. You need a private sale.
Be wary of auctioneers,as their costs have been known to our weigh your profits!
Use a reliable site to check any hallmarks etc, my mum always said her large silver locket dated to the 1700s,and I was like oooh special,rarely wore it, but when I checked it out it is the 1917 hallmark,so somewhere between 19…17 and 17…00s Chinese whispers someone got it wrong. Still it’s a nice piece, I just wear it more.
Originsl old boxes, and especially receipts are useful, and if a nice story attached, or any links to anyone or anything the interest can add more.
Any one buying a diamond under say 5 carats is wasting their money, you never get a good return on a diamond.
An older large stone is usually better than a small perfect stone, as it can be recut.
Matched sets usually do better.
Over wearing purer gold which is softer will likely result in wear than needs repair, mat3ching a link is hard, so do not buy tight necklaces or bracelets, in case just a single link is damaged not worn, wear usually effects all or say half the links, I have two necklaces that are worn in this manner and are basically gold weight only.
when putting jewellery into a store for repair, don’t post it!, photograph at several angles,and make sure they know you have done this, use the photograph to explain where you want the repair, thus they know you know exactly what it looks like and it better come back the same.
Always double check what they say if they start trying to cut the price with bullxxxx excuses.
Also when buying play careful, I once went to a jewellers that did second hand jewellery and there were a number of secondhand necklaces made from old watch chains, I saw the stone I wanted immediately, but realised it was on the thinnest chain, so I ummed and aughed then said if it was that stone and that chain I would take it there and then, and he swopped it to the heavier chain and did not charge me more…the other chain a much better weight
Citrine there is a small chip on thE corner I knew that when I bought it but the gem is bigger than my thumb and I like the dolphins motif the fob hangs from

I paid 10 pound for this in the 80s, only glass 1920s deco most of the cost was restringing,and it needs it again, but it’s a favourite piece I gave to my mum for Mother’s Day,she loved it to bits.
personally I prefer semi precious citrines,garnets,amethyst especially with pearls, I can’t afford a coloured diamond and the clear ones are just colourless.
Anyway history is everything I have a couple of cheap rings not worth wearing, but they are pre 1900s, one has lost its stones,but they are from our family,my boys won’t have any sentimentality on this, eventually my granddaughter might but I am not holding my breath,her mother has little sentimentality, just dollar signs

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Once we’re gone, my youngest boy will try to hold onto his stuff as a kid,but I doubt our stuff unless electronic will hold much interest. hopefully loads of stuff will end up in homes where they are cherished, there is a lot of not much value but has sone history.
The 1890s clock large cumbersome value barely more than 200 most years, who else cares my granddad was a bin man, and picked it up from a once nice house now a hotel with no heart.
Stones from the seaside, inc a unusual lizard rock from Cornwall once prolific by the water,but now all taken as they are curiosities where ancient deep rock had been thrown up by some millions old earthquake, it’s a rock.
glass bottle,wine hand made, found in the ground when a really old pub had an extension, amethyst amber pharmacy green my dad was a building control office and records showed no work there thus could have been 300 years old, but providence hard to establish, I suppose a glass historian might wet themselves.
ho hum