Decode HRD and AGS Certificate Numbers, the Less Common Labs

The labs nobody talks about

GIA gets all the attention. IGI owns the lab-grown space. But two other grading laboratories still show up across our database of 16 million diamonds from 100+ retailers, and their certificate numbers follow patterns that confuse even experienced buyers. If you've read our guide to finding hidden certificate numbers, you know how we decode GIA and IGI certs from retailer listings. HRD and AGS play by different rules.

HRD Antwerp grades a significant share of European inventory. AGS, once a respected American alternative to GIA, has largely been absorbed into GIA's operations. Yet legacy AGS graded stones remain listed across dozens of retailers. Both labs use numbering formats that overlap with retailer SKUs, creating a real disambiguation problem when you're trying to trace a stone back to its grading report.

HRD Antwerp and its numbering quirks

HRD (Hoge Raad voor Diamant) operates out of Antwerp, the historical centre of the diamond trade. European retailers favour HRD reports, particularly in Belgium, the Netherlands, and Germany. Walk into a jeweller in Antwerp's diamond district and you'll see HRD certs pinned behind every counter. Online, they're less dominant but far from rare.

HRD certificate numbers run between 8 and 12 digits. That's a wide range, and it's the source of most confusion. An 8 digit number sitting in a retailer's product page could be a legitimate HRD certificate number. It could also be the retailer's own internal SKU. There's no prefix or formatting convention that reliably distinguishes the two at a glance.

Longer HRD numbers (10 to 12 digits) cause fewer problems. Retailer SKUs rarely stretch that long, so a 12 digit numeric string in a diamond listing almost certainly points to an HRD report. The 8 and 9 digit range is where things get messy.

One thing HRD does well: their reports include a detailed light performance assessment that goes beyond what GIA offers on a standard report. If you're comparing an HRD graded stone against a GIA graded one, the grading scales align closely on the 4Cs, but the supplementary data differs. HRD also grades lab-grown diamonds, so you'll encounter their reports on both natural and synthetic inventory.

AGS is gone. Its diamonds aren't.

The American Gem Society Laboratories earned a strong reputation for cut grading. Their "AGS Ideal" designation became shorthand for exceptional light performance, and serious buyers once sought it out specifically. AGS certificate numbers are 10 digits long and begin with 104. That prefix is the giveaway.

See a 10 digit number starting with 104 in a diamond listing? You're almost certainly looking at an AGS report. No major retailer SKU system we've encountered uses that pattern, which makes AGS numbers easier to identify than HRD ones.

AGS merged its laboratory operations into GIA in recent years. New diamonds don't receive AGS reports. But thousands of AGS graded stones still circulate in retailer inventories, some listed for years, others recently acquired from estate sales or secondary markets. When you run one of these through our certificate decoder, the 104 prefix lets us identify the lab instantly.

One wrinkle worth knowing: AGS used a different cut grading scale. Where GIA grades cut as Excellent, Very Good, Good, Fair, and Poor, AGS used a 0 to 10 numeric scale, with 0 being their highest grade (AGS Ideal). A stone graded AGS 0 in cut is roughly equivalent to GIA Excellent, but the systems aren't perfectly interchangeable. Keep that translation in mind if you're comparing an AGS graded stone against GIA graded inventory.

When an eight digit number could be anything

This is where our decoder earns its keep. Picture a diamond listing showing an 8 digit numeric code. That number could be:

An HRD certificate number. Plausible, since HRD uses 8 digit numbers.

A retailer's internal SKU. Also plausible. Many retailers assign 8 digit product codes.

A truncated or reformatted number from another lab. Less common, but it happens when retailers strip leading zeros or drop prefixes during data imports.

With GIA's 10 digit format and IGI's conventions, our decoder can usually make a confident match on pattern alone. Both the GIA decoder and IGI decoder benefit from more distinctive numbering. HRD's 8 digit certificates don't give us that luxury.

We built a disambiguation flow for exactly this scenario. When an 8 or 9 digit number hits our decoder and we can't confirm the source from surrounding data (retailer name, listed lab, other context on the page), we ask you which lab it belongs to. Not a failure of the system. It's the honest response to genuine ambiguity. Any tool claiming to resolve every 8 digit number automatically is guessing, and guessing wrong sends you to the wrong report entirely.

What the market data shows for these labs

Most of our databaseed diamonds carry GIA or IGI reports. HRD and AGS represent a smaller but meaningful slice, concentrated in specific market segments. HRD graded stones appear most often in European retailer feeds. AGS graded stones cluster in US inventories, typically from retailers who specialised in premium cut quality before the merger.

Pricing across the broader market gives useful context for why cert verification matters. Natural diamonds still command substantial premiums over their lab-grown equivalents across every shape we track.

Those gaps matter when you're verifying a certificate, because knowing whether a stone is natural or lab-grown changes the price expectation entirely. An HRD graded natural oval averaging $7,411 sits in a completely different bracket from a lab-grown oval at $1,406. If a retailer lists an HRD number on a stone priced at $1,400, you should be asking whether that report actually matches the stone being sold.

Cross-retailer price variation adds another layer. For the same natural oval, we see average spreads of around $84 with cross-retailer savings potential near 37.6%. Natural cushions show spreads around $80 with savings potential of 25.5% across retailers. Shopping across sellers for the identical stone (same cert number, same physical diamond) consistently reveals meaningful price differences. That's precisely why decoding the cert number matters: it's the only reliable way to confirm you're comparing the exact same stone at two different prices.

Where you'll encounter each lab

HRD graded stones turn up most frequently on European platforms and retailers with strong Antwerp supply chains. Shopping at a Belgian, Dutch, or German online jeweller? Expect HRD certs alongside GIA. Some international retailers carry a mix, with HRD comprising a noticeable share of their natural diamond inventory.

AGS graded stones are harder to find in new listings but still present. Look for them at US retailers who built their reputation on premium cut quality. Stores that marketed heavily on "AGS Ideal" or "triple zero" diamonds sometimes still carry AGS graded inventory, even though new reports now come from GIA. Secondhand and estate diamond sellers are another common source. A five year old engagement ring with an AGS report is still a valid, graded stone. The report doesn't expire just because the lab changed hands.

You won't find lab-grown diamonds with AGS certs. The lab stopped issuing new reports before lab-grown went mainstream. HRD does grade lab-grown stones, though, so you may encounter HRD reports on both natural and lab-grown inventory. Marquise lab-grown diamonds show a striking 85.8% gap between natural and lab-grown average prices. Whether the stone is graded by HRD or IGI, that gap stays enormous.

Where HRD and AGS go from here

Two quick rules of thumb. If the certificate number is 10 digits and starts with 104, it's almost certainly AGS. If the number runs 10 to 12 digits and appears alongside European retailer data, HRD is the likely source. Eight and nine digit numbers without other context genuinely require disambiguation, and our decoder will walk you through that rather than guess.

The lab printed on the report doesn't change the diamond. But it changes how you verify specs, how you compare prices across retailers, and whether you can cross-reference the stone in our database. With AGS no longer issuing reports, the pool of AGS graded stones will slowly shrink as older inventory sells through or gets regraded by GIA. That 104 prefix will become rarer every year.

HRD isn't going anywhere. Antwerp's lab continues to grade both natural and lab-grown stones, and European retailers will keep listing HRD numbers for the foreseeable future. If anything, we expect HRD graded lab-grown stones to grow as a share of European listings.

Our decoder handles both labs. Paste in the number, and if it's unambiguous, you get the lab and report link instantly. If it isn't, you get an honest question instead of a wrong answer. That's the trade we made, and we think it's the right one.