Bimetallic

That's strange behavior, though I know people who would make the bad "sucker" joke in a way that wouldn't be meant as an insult. There's a personality type that would think that it was an innocent, throwaway joke, not meaning it seriously. There are all kinds of people out there, and some jokes don't do as well in various mediums, like email. He might be one of those people, thinking it was funny but not insulting, or maybe he really is a jerk. The fact that you never posted your end, or the full thread, gives me some pause, since people repeatedly requested it. From what I see, you only paraphrase your end of part of the thread, I think your first reply to his reply. We can't really know anything about this situation without seeing both sides, not just one side. On the price issue, there's no such thing as a "fair price" in the sense of someone else being obligated to agree that it's fair, much less agree to the price. Humans have a rich psychology around price and trade and sometimes this wobbly concept of "fair price" (which people use in a lot of different meanings). If someone doesn't agree to an offered price, there's no point in complaining that it was a "fair price". It doesn't add any information to our understanding of a situation or attempted transaction. This reminds me of people who talk about wanting retail silver to reach its "true" price (they usually call it "physical" silver, but they're exclusively referring to retail silver specifically, not physical as purchased by industry or anyone else). It's already at its true price, since the market price is the only true price, unless we think there's some kind of broad manipulation of retail silver, a tiny market that hardly anyone cares about. In this case, a seller's behavior is a big clue to how "fair" or "true" a price is. Since he didn't accept the price, it's likely that he's able to sell them at his listed prices (or he thinks he can, and he'll either be right or wrong about that). So it doesn't mean anything to say a price is "fair" if the market is carrying along at a much higher price. (Buyer behavior is also a clue to fair or true prices. Your rejection of his price could've indicated that it was too high if you were able to get it for your price elsewhere, or if he wasn't able to sell any at his listed price, but that doesn't seem to be the case here.) You offered more than 20% over spot, which seems like a lot for gold, even in this market, but I guess those guineas are going for much more. (They were out of stock at Bullion by Post and Chard's when I looked.)

Very nice. That looks like an excellent result. I didn't know that such services were readily available. How much does it cost? I'm not familiar with that coin. Do they not have years, or is the year encoded in some of those letters? What's the composition here – pure gold or Crown gold? I didn't know that gold could have that kind of tarnish, or whatever we'd call the discoloration in the Before photos.

If the range is 8 inches, why not try testing coins sideways, across their longest dimension? Silver one-ouncers are all around 40 mm in diameter, or about 1.57 inches. That way you don't have to worry about their surface features. If it can't test coins, it seems pointless, since all coins have "patterns or designs". Why can't ultrasonic testers test Crown gold alloy, e.g. the American Gold Eagle? What does ultrasound know about "purity"? It's just a velocity like any other velocity, right? Doesn't the 22 karat alloy used in the Eagle have a characteristic velocity like any other metal? Your table includes brass and stainless steel, which are also alloys, and somewhat less pure than Crown gold (stainless has at least 12% chromium and usually 8-10% nickel, among other things, while Crown gold only has 8.3% non-gold constituents). The Eagles have had the same composition of gold, copper, and silver from their inception, so I don't know why they can't be characterized for testing purposes. (It's a different alloy than other Crown golds, like the Krug, which has no silver, just copper. This is why Eagles are a much prettier color than Krugs. I don't remember if Sovereigns have any silver.) By the way, what does the Royal Canadian Mint "Bullion DNA" method do exactly? Is it just a high-res photograph/scan of unique imperfections or something, like the PAMP Suisse authentication system? It's a bummer that we still don't have reliable, simple, and affordable testing tools for bullion at this point in history. I would've thought that a smartphone could be leveraged for such purposes. I don't understand why spectroscopy isn't more affordable at this point.

What's a "car boot" in this context? I thought it was the British word for a car trunk, but it seems to mean something else here.

Silver is the worst by far. Then: Copper Aluminum Gold Osmium Note that aluminum is usually made into alloys with magnesium, zinc, silicon, and sometimes copper and other metals. Pure aluminum isn't used as much as the alloys are, and the alloys vary in their corrosion resistance. Osmium is super rare, hardly used in the world. Stainless steel's corrosion resistance varies depending on the type of stainless alloy it is. It's like aluminum. There is nothing simply called "stainless steel" – it's always a specific grade/alloy. They all have double-digit percentages of chromium, and one of the usual differentiators is whether they have nickel as well, and how much nickel. Nickel enhances their corrosion resistance, and the common 304 and 316 have quite a bit, especially the latter. 316 also has molybdenum, which helps too. Another approach to better corrosion resistance is to add nitrogen, and you see this in some stainless knife steels. You can achieve good corrosion resistance without any nickel if you have nitrogen and maybe better control over the process. The cheapest stainless has no nickel, e.g. the 400 series (nickel is super expensive at over $8.00 per pound). Like 430 stainless, which is what Mexico makes all their circulation coins from. It's not as corrosion resistant as the 300 series with all their nickel, but it's good enough for a lot of purposes, like coins evidently. Smart mints use steel for coins, not expensive nickel and copper as base materials, with the big differentiator being whether they plate cheap mild steel with nickel (or layers of nickel, copper, and nickel again, like the Royal Canadian Mint) or whether they use stainless and don't bother with plating. It's a trade-off with the cost of the chromium in stainless steel, vs the lower material cost of plain mild steel but then having to plate it in nickel and copper.

That article is bogus. All their photo examples are non-pure gold, while talking about pure gold's properties... The American Double Eagle coin they feature is only 90% gold, balance copper. The Krug is 91.7% gold (Crown gold), balance copper. So what are they talking about? It's weird. Their Roman example might be 99% gold, but it varied and lots of emperors issued those coins for a roughly 400+ year period. I wouldn't expect modern standards of quality control with 2,000 year old coins, even Roman ones...

Always use troy ounces for precious metals. Conveniently, there's an exact conversion from troy ounces to grams because of the International Yard and Pound Agreement from the 1950s. By that agreement, a troy ounce is exactly 31.1034768 grams. As others noted, a kilogram is 1000 grams / 31.1034768 grams/oz t. So it's 32.15075 troy ounces. That's slightly different from the above offered values because I used the correct, exact value of a troy ounce. I don't like rounding errors. Unfortunately the result probably goes on forever, so you have to cut it off at some point.

This will make you underestimate the amount of gold or silver. When bullion is marked as a given weight of PM, the object will contain at least that weight of the pure metal, not 0.999 or 0.9999 of the marked weight. Meaning, the object is always slightly heavier than its marked weight. The fineness refers only to the purity of the object, not to the amount of the precious metal. That's key. This is also why Crown gold (.9167 fine) bullion like Sovereigns, Eagles, and Krugs, and Britannia silver (.958 fine) bullion always contain the marked amount of actual gold or silver, not a fineness fraction of it. Also, the stated fineness should always be an understatement, a minimum. Silver marked as 999 won't be precisely 999000 fine. It will more likely be something like 9995, and it will vary some from batch to batch.