Another for the hoover!

Little Irish Henry 111 quarter, only minted for 3 years 1251-1254, a solid 9 on the Nox, pleased with that.
The dime gives you the scale.

Thats a rather nice cut 1/4 was that with the stock coil or one of the others ?? not sure why but not as yet taken with the stock coil i have mainly been using the 6'' for about 90% of the time and occasionally with the 15'' coil.

Just the stock coil mate.

Serious piece of history!
Your photos are phenomenal. Really puts things (sizes) into perspective.
How thick is that little sliver of silver..... especially compared to the dime? (I'm guessing.... about 1/2 the thickness).

Tom's right about your photo's, the 'coin in hand' pic has great depth of field.
The mean thickness of a dime is about 1.0 mm ( 0.95mm? ) , the medieval penny about 0.3 mm. But in the hand, it's more pronounced, as the dime has a thick edge, making it appear 1.25 mm, and hammered coins would tend to wear on their edge in circulation. They look more like a 5:1 ratio.
Target 'corner frequency' of a typical cut quarter penny is 25kHz. The popularity of XP's 18kHz GoldMaxxPower was largely due to its ability to find such coins.

Thanks folks, this quarter has got little wear compared to some of the hammereds you find.
Here's a few more pics on the thickness and weight beside a barber dime.
Thats quite interesting Pimento on the best khz for the target, but how the heck do you work something like that out??

Working out target frequency?
Well, the simple answer is: you measure it. You can't "work it out", really, as the electrical conductivity of the corroded silver is unknown.
By poking about inside a suitable detector with a decent voltmeter, you can measure the residual signal levels when there's no coin present, then measure the signals given with a coin near. The difference is that caused by the coin. A bit of fairly simple maths allows you to calculate what phase lag the coin gives, and then work out the coins 'corner frequency' / '-3dB frequency'. The phase lag is essentially what the target ID is indicating, in an engineered way ( squashed and stretched to make it more useful). So it's also possible to calibrate the target ID scale of a machine, so you could simply translate "61" to "5 kHz", "18" to "33 kHz" etc.

Target corner frequency is inversely related to the linear size of a thin target like a coin. So if you doubled the diameter of a coin, its corner freq would halve. So a typical full-size 18mm hammered coin has a corner freq of about 13kHz. Quartering the coin is pretty much the same as making it a 9mm diameter circle.(same area, roughly the same shape)



Edited 1 time(s). Last edit at 09/08/2019 10:46AM by Pimento.

nice!