Coinshooting machines do a fairly good job of detecting rings because of their size and roundness. However, there's a big difference between detecting gold rings and detecting natural gold nuggets. The good news is that any metal detector will find the larger nuggets. The bad news is that the overwhelming majority of natural gold is small stuff, usually in mineralized soil, and won't be detected by a machine designed primarily for coinshooting.
Frequency isn't the whole story, but it does matter. Real gold machines run from 13 kHz (Tek T2) up to 71 kHz (GB2). Our F5 and Omega which run at 7.8 kHz have a computer assisted ground balanced autotune mode which is suitable for casual gold prospecting. A person swinging an F5 or Omega who knows what the heck they're doing, is going to find a lot more natural gold than someone with a high end gold machine who doesn't know what they're doing. Knowledge and skill are far more important in gold prospecting than in coinshooting, where even a newbie with an entry level machine can easily find stuff.
The BH 3300 platform machines allow searching in static all metals mode with manual ground balancing, and are fairly sensitive. With enough skill it might perform at about the same level (in gold prospecting) as the F5 and Omega. However the lack of computer assisted ground balancing and autotune mode means that developing the necessary skill in the use of the machine would take a long time.
Anyone who contemplates gold prospecting, I recommend reading my my book Gold Prospecting with a VLF Metal Detector, online in .pdf format at both the Fisher and Teknetics websites.
--Dave J.