Using low discrimination settings.

This time last week I was searching along the banks of the Mississippi river, you just cant keep me away from the water no matter where I go. 
The axe head in the photo is from the early 1900s, and as you can probably tell by the iron find I was not using any discrimination. 

I always prefer to use little to no discrimination when searching around inland rivers and lakes, even though iron objects lost around freshwater do not corrode as fast as iron objects lost around saltwater. 
At Florida saltwater beaches I prefer to use a little discrimination to help me identify "Iffy" targets on very trashy beach sites. 
For example, the Discrimination setting of three on the Minelab Excalibur is low enough to help identify corroding bottle caps but not too high that you miss 10K gold rings. 
On the new Minelab Go-Find 40 and 60,  removing the iron icon allows you to avoid digging corroding bottle caps, but not miss 10K gold rings. 
The amount of discrimination you choose to use is up to you, but on every VLF metal detector I have used the 10K gold drop out level is the maximum level I will set the discrimination to. 
I always advise people to choose a metal detector and a search mode ( all metal or discrimination) that best suits the beaches they metal detect at. 
Sometimes, there are certain beach or water hunting situations where you can use both search modes. For a beach or water hunter who spends the majority of their time metal detecting at touristy beaches, its a no brainer to use the 10K gold ring drop out discrimination level. 
Set your metal detector discrimination control to slightly under that 10K gold ring, if you still worry about missing a good target. 
Using a slightly elevated discrimination control setting, will also allow you to find hot spots on the beach or pick up a coin line faster.  
A slightly elevated discrimination setting works for me and it could work for you, it all depends on the beaches you metal detect at. 
On heavily hunted beaches, every iffy or bad target you can positively ID through experience using your metal detector and not dig, puts you one step closer to finding those good targets you want to dig.