Quick Answer: Target ID is a number a detector displays to estimate what kind of metal is buried before you dig — Garrett’s AT Pro uses a 0-99 scale, while Minelab’s Equinox line uses a VDI scale running roughly -9 (iron) to +40 (high-conductivity metals like silver). On the AT Pro, a nickel and a pull tab both commonly land in the 52-53 range, according to High Plains Prospectors’ published target ID cheat sheet — which is exactly why the number is a strong clue for deciding what to dig first, not a guarantee of what’s in the ground.
Every detector with a numeric or segmented display is doing the same basic thing: measuring how a target’s electrical conductivity bends the coil’s signal, then mapping that reading onto a scale. The scales aren’t standardized across brands, the numbers shift with depth and target size, and the two metals hunters most want to tell apart — nickel and aluminum pull tabs — happen to read almost identically on most machines. Understanding what the number is (and isn’t) telling you turns target ID from a guessing game into a real digging-priority tool.
How target ID numbers actually work
A detector’s coil reads a target’s conductivity, not its identity. Metals with high conductivity — silver, copper — bend the signal one way and report high on the scale; poor conductors like iron and most foil bend it the other way and report low. Everything in between (nickel, gold, aluminum, brass) lands somewhere in the middle, which is exactly where the overlap problems start.
| Scale | Used by | Range | Iron/ferrous zone |
|---|---|---|---|
| 0-99 numeric | Garrett AT Pro | 0 to 99 | Low end of the scale, refined further by 40 iron-discrimination levels |
| VDI | Minelab Equinox 600/800/900 | -9 to +40 | -9 to 0 (ferrous); 1 to 40 is non-ferrous |
| Icon/segment only | Garrett ACE 200/300/400, most sub-$200 machines | No raw number shown | Icon-based (coin, ring, iron) instead of a digit |
On Minelab’s Equinox, a nickel typically reads around VDI 13, a dime around 26, and a quarter around 30 — numbers experienced Equinox users have compiled through repeated field testing and shared in the Equinox community. Those numbers only apply to Minelab’s scale; running a Garrett detector, the same coins report on a completely different 0-99 range.
Garrett AT Pro — 0-99 Numeric Target ID + 40 Iron Levels
- Full numeric target ID from 0 to 99 gives more resolution than icon-only entry machines, per Garrett's own AT Pro documentation.
- 40 levels of iron discrimination let hunters fine-tune iron rejection separately from the target ID number itself — useful in nail-heavy relic sites where the ID alone isn't enough.
- Pull tabs and nickels commonly overlap in the 52-53 range on this machine, so our own coin hunting guide recommends digging both rather than trusting the ID to sort them.
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Minelab Equinox 900 — Multi-Frequency VDI, -9 to +40
- Multi-IQ multi-frequency scanning feeds the VDI number, which the Equinox community has field-mapped to roughly nickel≈13, dime≈26, quarter≈30 through repeated testing.
- The -9 to 0 ferrous band and 1-40 non-ferrous band are a cleaner conceptual split than a single 0-99 scale, but the numbers themselves don't translate to Garrett's scale at all.
- Community-documented limitation: a pull tab can be made to sound like a dime under certain ground and depth conditions, which is why our Garrett vs Minelab comparison treats target ID as a supporting signal, not the final word.
Why target ID isn’t a substitute for digging
Three real-world factors shift the number a detector reports, even for the exact same object:
- Depth — a coin sitting deeper in the ground returns a weaker, less precise signal, which can pull its target ID toward the noisier middle of the scale even though the coin itself hasn’t changed.
- Size and orientation — a large piece of crumpled foil can mimic a coin-range reading, while a thin gold ring can under-report and land closer to a pull tab’s number than to a “jewelry” ID.
- Ground mineralization — hot, mineral-rich soil adds noise to the same conductivity measurement that target ID is built on, which is one more reason our ground balance guide treats ground balance and target ID accuracy as directly linked, not separate topics.
That’s why every serious buying guide on this site — from the beginner’s guide to the silver hunting guide — frames target ID as a tool for prioritizing what to dig first, not a filter for deciding what to skip. Skilled hunters routinely dig “maybe” numbers precisely because the nickel/pull-tab overlap and depth-based drift make a clean digital number report look less certain than the display suggests.
The bottom line
Target ID numbers are real, useful, and consistently misunderstood. A 0-99 reading on a Garrett or a VDI reading on a Minelab is a genuine estimate of conductivity, refined further by iron discrimination and (on multi-frequency machines) simultaneous multiple readings — but it’s still an estimate, not an identification. The most reliable use of the number is exactly what field-tested hunters already do with it: let a mid-range number like 52-53 on the Garrett AT Pro or a low-20s VDI on the Minelab Equinox 900 move a target up the dig-priority list, then confirm with a shovel instead of a screen.