Silver Content of 1967 Canadian Quarters A free definite test 1967 cents are either 80% silver, like earlier years or 50% silver, like 1968. There has been no way to tell the difference, without resorting to x-ray fluorescence: but I think I’ve found a way (using a free phone app). Various subjective tests are suggested (sound when flipped, color, brightness under a tissue....) but they produce unconvincing results. I took the “sound” idea and tried to confirm it on my phone. I’ve accumulates a load of silver quarters which I now want to sell: and 14 are dated 1967. I also have some earlier dates and some 1968 coins. So here’s what I did. I have an free app on my phone called “physics toolbox sensor suite” which has a lot of useful sub-apps. (I'm sure other similar apps could be used) One of the sun-apps, under the ‘accoustics’ heading, is called spectrum analyser. It produces a picture of the noise my iPhone can hear at any moment. It plots the ‘intensity’ against frequency. A ping (from flipping a coin) should show as a sharp peak at a frequency. If people are right that silver content affects the tone, then the 80% and 50% coins should have different peak positions. I put my coins in 3 piles: before ‘67, 67 & 68. Testing I set my phone on my floor with the speaker pointing away from me. I had one hand ready to compress (simultaneously) the ‘volume up’ and ‘off’ buttons on the sides of my iphone (to screen capture) and in the other, I was ready to flip a quarter. I flipped the coin and pressed the buttons to screen capture the ping. Next I looked in my “photos” to see what the acoustic spectrum looked like. The key area is at the extreme right of the chart (above 10 kilohertz). Results The background (quiet) chart is image 1. The yellow highlighted area (around 10 kHz) is where the action happens. (I For 1966 and before, the chart was always like images 2 or 3. There’s a characteristic peak at 15khz and also peaks at 12hz &/or 7hz For 1968 it was always like image 4, with a characteristic peak at 17hz. The intensity of the peaks varies but the position of each peak is reliably constant. So, I got out my 14 x 1967 quarters and found 12 were 80% silver. The mintage figures suggest 52% of the coins were minted using 0.800 silver: but maybe I’ve been lucky, or got several coins from a single early mint roll? Conclusion It is possible to distinguish, definitively, 80% and 50% silver Canadian quarters, using a free app. (Well done to those who detected a difference by ear: You were right!) The accoustic app technique could presumably be used for other coins (or to reveal fakes) but the coins would need to be in collectible condition and similar coins of known composition would be needed to calibrate the test (like I’ve done for the 67 quarter). I’d be interested to hear any thoughts on the test and particularly any issues or successes using it. ScotsJohnR Sent from Outlook for iOS
Interesting experiment, thanks for sharing! Though, I regret to add that I’m against any diagnostic that requires striking a coin.
