Melon

Well my Silver Una turned up today and.... 😭😭😭
Smashed capsule and the scratch to the right of her head is on the coin. Oh dear. 

Well my Silver Una turned up today and.... 😭😭😭
Smashed capsule and the scratch to the right of her head is on the coin. Oh dear. 

Well my Silver Una turned up today and.... 😭😭😭
Smashed capsule and the scratch to the right of her head is on the coin. Oh dear. 

Well my Silver Una turned up today and.... 😭😭😭
Smashed capsule and the scratch to the right of her head is on the coin. Oh dear. 

Direct from Royal Mint. Assuming they'll sort it, but a bit disappointing after the long wait. I've sent them an email. 

Well my Silver Una turned up today and.... 😭😭😭
Smashed capsule and the scratch to the right of her head is on the coin. Oh dear. 

https://feedback.ebay.co.uk/ws/eBayISAPI.dll?ViewFeedback2&userid=davidw9591&&_trksid=p2047675.l2560&rt=nc&iid=293393164065&sspagename=VIP%3Afeedback&ftab=FeedbackAsSeller
First confirmed feedback of Gold Una & Lion sale from the £18,000 on  Boxing Day, i presume he got the coin and not just an empty lunchbox ! 

I didn't even edit this one.
What on earth are the Royal Mint doing with their website... Availability changed, 205 or 225 mystery, price reduced randomly to £3,835 - all on a coin that hasn't been available for ages now. Who manages this website and don't they have better things to be doing?! 😆

My setup was pretty rough to be honest. The scales I have that are accurate to 3 places but only weigh up to 50 grams max (pocket sized), so the water container has to be very small. Other than that it's just dipping in water. I was careful to not touch the sides and be completely submerged when taking the reading, although movement in the water does cause a fair bit of variation but I tried to get the weight at rest. 
I've seen handing water baskets on YouTube that I think would be a good investment, but can't find them online anywhere. I think I'd like to get a half decent setup that doesn't take forever to use, as this seems like a very useful test going forward. 
One thing I looked at was extrapolating the result of the Maple onto the others - so to get the Maple down to the expected result of 19.32 I would need to divide by 1.047. If I apply that same metric to the other readings (essentially assuming a consistent level of inaccuracy) then the sovereigns would score as follows; 
1982: 17.66 (good)
1903: 17.05 (low) 
1915: 17.45 (good) 
That would suggest 20 carat gold for the 1903. But clearly that's not a very accurate approach! 😂
A very worthwhile watch, thanks. I think this one is going to go back next week when they reopen, will be interesting to see if they're cool about it. 

I didn't even edit this one.
What on earth are the Royal Mint doing with their website... Availability changed, 205 or 225 mystery, price reduced randomly to £3,835 - all on a coin that hasn't been available for ages now. Who manages this website and don't they have better things to be doing?! 😆

First purchase of the year for me and what a way to start! Still waiting on coins to arrive from December purchases so can’t wait to put them all in received section

Not really a valid "calibration" as the maple weighs twice as much as the half sovs. The standard deviation for the sov measurements is likely to be substantially higher than the maple.

I really like your approach of extrapolating the maple data, it does seem the 1903 is too suspect.
Given all the other observations I would hope HGM replace it for you. 

My sacle with the same accuracy weighs up to 200 g and even with that the water container needs to rather small. I'm only guessing but I think this very small water container might be the cause for the inacurracy.
I have tried this threadless method too but without any specific water basked, basically just a random can, hanging under the sacle, inside the water. That was a friend's scale though, mine would have been unsuitable for this method.

It’s the first week and I seriously doubt am going to top these with anything cooler this year. 
 
Franklin Mint Sterling Silver Star Trek Spaceships- missing one out of the 12. 

First gold purchase alert! 
Ok, so it's only a 1/10th Britannia - but my toe has officially been dipped into the golden water. I didn't expect such intricate detail. Will definitely be looking to add more gold now i've taken the plunge. 
Shout out to @ilovesilverireallydo for the Black flip suggestion on another thread. 
 

Really interesting info and the 1903 coin stands out form the norm again. I was watching this recently, https://www.youtube.com/watch?v=U5aKYCKrUG4 , (How to Identifiy a fake sovereign - Chards). Seems like there a fakes out there at 21ct, which could explain the relative difference on the 1903.
 

From my experience, not that much, I too thought maybe the accuracy goes down with half sovereigns (at at time when I only had one half sovereign, the rest of what I had was all full sovereigns). I turned out it was not the string but it was fake indeed, 18K Gold, as mentioned in other threads, before.
I have used dental flosses and thought, maybe that's too big threads but I don't think it is, even for half sovereigns. If you used normal sewing threads, it will impact the accuracy even less.
Having said that, you must have made something wrong, your control object, the quarter maple, is way off which makes all the other results questionable, in my opinion.
What was your exact set-up?

Don't be put off by a minor set back, put it down as a minor set back, good learning experience and carry on enjoying collecting sovereigns.

The odd mark on the top of the 1915 is intriguing....would be interested if this turns out to be a genuine coin it’s a mint error or a cast counterfeit if you have it graded. 
 
best
Dicker

If you do decide to sell these to any of the main dealers as gold, a spot of advice, did you see what I did there... Make sure you state that the coins are not genuine, if you don't they may not honour the price they quoted you. I have had this issue, they quote one price and then when they receive them give you another as they aren't genuine... Its just a scam really, lots of the coins they take in as bullion get sold for a premium, and its nothing to do with the gold content! if not clear let me know and I'll elaborate. 

If you are near Hatton Garden pop into HGM - I think they have a machine which will test whether the coin is 22 ct.

The 1.9% that the 1903 is above standard diameter equates to almost 3% in area, and therefore would be expected to weigh almost 3% more (or 4.1g) than standard assuming 22ct. Its true weight of 3.926g is actually higher than I would expect given the amount of wear on the coin. Although this is actually contradictory evidence and may well support it being 22ct or pretty close, the discrepancy between size and actual weight strongly suggests it being a forgery. Add in the poor quality of the details, it’s pretty conclusive.
I’m leaning toward the 1915 being genuine. It is slightly too big but not much, could be due to prominent edge milling. The weight is consistent with a coin in very good condition with little wear. The only thing that worries me is the flatness of the chest which is out of keeping with the wear on the rest of the reverse. As I have said before, I have seen this before on other branch mint halves. Maybe they had a problem with weak striking, the gold from the chest detail could have gone into that deep die crack? The fact there is a die with such a deep crack suggests it was a well used and worn die.
One thing I have found is that measured thickness is a poor indicator. It’s very difficult to measure accurately and I don’t think it correlates very well with published data. As the OP has found, The measured variance is simply too great.

Great data bomb, though looks like it doesnt solve the matter.  The extra thickness of the 1915 would indicate ~10% extra material, but weight is on spec. This, along with other outliers, leads me to conclude the measurement is suspect (and it is difficult with coins).  If they are fake they are not the usual obvious ones, except that odd "scratch" on the 1915.  Assuming the dealer checks stuff coming in, i'd reckon they contain the expected amount of gold, even if they are copies.