Rum is rife with historical imagery of its colonial past—of merchant ships crossing the Atlantic, carrying rum casks destined for European ports. London’s docks were a common destination in the 18th and 19th centuries, where rums from Britain’s Caribbean colonies were aged and blended to create the famous Navy-style rum (an overproof blend from several colonies), which kept the empire’s sailors fortified.

But London was far from the only destination for Caribbean rum—France, Spain and Germany all imported their fair share of rum casks as well. Over time, the fortunes of rum trading ports waxed and waned, and by the 1970s, Britain’s naval rum tradition was all but extinct. By then, Europe’s rum trade had a new capital: Amsterdam.

The company at the heart of Amsterdam’s modern dominance of the European rum trade is E&A Scheer, which has been operating continuously since 1762. Their primary business is supplying rums to brands who lack their own distillery, or who want to combine rums from several distilleries to make a unique profile. At any given time, Scheer has several million liters of stock from 25 to 30 distilleries on hand, including what is likely the world’s largest store of ultra-funky, high-ester Caribbean rums.

Scheer’s headquarters sits along Amsterdam’s famous canals, behind the ornate wooden door of an otherwise traditional three-story row house. Through the doorway, a small room within holds rum Valhalla: hundreds of clear glass sample bottles, categorized and labeled, filled with cane spirit from Jamaica, Barbados, Guyana, Cuba, Martinique, Brazil and Indonesia, among others. From this room, a small team of blenders works with samples, trying out different combinations and ratios of rums to achieve the customers’ target flavor profile.

Despite sales of around 35 million liters per year—which makes them the fourth or fifth largest rum enterprise in the world, somewhere between Appleton and Bacardi—very few people have ever heard of E&A Scheer. They sell no rum under their own name, leaving the spotlight to their customers who purchase Scheer’s blended rums and market them as their own. The odds are high that you’ve probably had multiple E&A Scheer rums without knowing it.

Of the brands that have chosen to disclose their relationship with Scheer, Denizen is perhaps the most famous. Their Merchant’s Reserve blends rums from several Jamaican distilleries with immensely funky grand arôme-style rum from Martinique to approximate the rums used in the classic 1950s Trader Vic Mai Tai. When Denizen conceived of the idea, they consulted with famed San Francisco bartender Martin Cate and chose Scheer for their blending expertise. The same is true for Richard Seale of Foursquare Rum Distillery, one of today’s breakout stars in the category, who sells his bulk rum only to E&A Scheer.

“Scheer’s role cannot be underestimated,” says Seale. “It was not practical for small brands and independent bottlers to all travel to the Caribbean to select casks, so Scheer brings the casks to them.” But they are not just middlemen, he says: “They are blenders.”

While their range of blending stocks enables a wide gamut of flavor profiles, one element they’re exceptionally well-versed in is ultra-funky rum. The nose, which recalls overripe banana, pineapple and petrol, is catnip to rum enthusiasts—the sugar-cane spirit equivalent of peated Scotch whisky. Open a bottle of Smith & Cross if you need a primer—that’s Jamaican funk with a capital “F.”

While Jamaica is synonymous with funky rums, they’re not the only game in town. Martinique’s Le Galion distillery makes molasses-based rums, including a grand arôme marque that holds its own with Jamaica’s funkiest. And on the other side of the globe, France’s Réunion Island also makes a pungent grand arôme. It’s no surprise that Scheer has stock of them all.

These funky rums aren’t produced in large quantities, partially because they’re time consuming and difficult to make (fermentation alone takes weeks). They’re also rums that are hard to market in large quantities given their pungent flavor profile—particularly those that use “muck” in their recipe. (Often mischaracterized as “dunder,” muck is a huge slug of acids added to the wash to supercharge ester formation.) Combined with pot-still distillation, it’s an intensely old-school way of rum making, but the payoff is a remarkably pungent product.

This artisanal rum-making tradition largely remains viable because Scheer purchases in bulk to use small quantities in custom blends. As Scheer’s managing director, Carsten Vlierboom puts it, “Many producers like working with us as we provide a wide audience for their rums and direct cash flow for large volumes, which might be hard to sell through their own brands.”

While Scheer does not disclose who their customers are, and most brands—with few exceptions—are likewise mum about their sourcing, rum geeks have become adept at identifying which brands E&A Sheer have had a hand in blending, mostly based on the rum’s description. In particular, rums that are a blend from multiple countries or claim a distillery source that they do not operate are often the product of E&A Scheer blending. Here are a few that are known to be sourced from the Dutch master blenders.

Denizen Merchant’s Reserve Denizen’s tagline is “Free the flavor,” which they do by making multi-dimensional rums sourced from at least two countries. Their Merchant’s Reserve combines rum from several Jamaican distilleries, as well as the molasses-based grand arôme from Martinique’s Le Galion, to craft the ideal rum for a classic Mai Tai. Price: $29

$29 ABV: 43 percent Purchase

Ron Dos Maderas PX 5+5 Williams & Humbert, one of the largest Spanish sherry houses, buys a blend of Barbados and Guyanese rum, already tropically aged for five years, from E&A Scheer. It’s then solera-aged for another three years in their palo cortado sherry casks, followed by two more years in ultra-sweet Pedro Ximénez casks. The resulting rum is on the sweeter end of the scale. Price: $43

$43 ABV: 40 percent Purchase

Gunroom Navy Rum Sweden’s Gunroom Spirits worked with E&A Scheer to develop a high-octane, Navy-style rum that’s quite different than Pusser’s, the best known in the category. Gunroom’s blend includes rums from Guyana, Barbados, Trinidad and Jamaica, all once British colonies. A fifth “secret” ingredient is known to be Batavia arrack, a pungent cane spirit made in Indonesia and considered a sibling of Caribbean rum. Price: $50

$50 ABV: 65 percent Purchase

The Duppy Share Caribbean Rum In the Caribbean, a “duppy” is a ghost or spirit known for mischievous pranks. The U.K.-based Duppy Share rum pays homage to the rum that “mysteriously” disappears from the cask during aging, presumably taken by duppies (rather than the angels). It’s a blend of Jamaican rum from Worthy Park Estate and Barbadian rum from Foursquare Rum Distillery. Price: $41

$41 ABV: 40 percent

By the Dutch Batavia Arrack Batavia arrack is a pot-stilled Indonesian cane spirit that predates rum; its primary difference is that Batavia arrack also includes red rice early in the fermentation process. At one time, its funky, pungent flavor was more sought after than that of rum, and today, E&A Scheer is essentially the only market in town for buying it. By the Dutch’s take contains liquid aged up to eight years, which is substantially more refined than the younger Batavia Arrack Van Oosten. Price: $62

$62 ABV: 48 percent Purchase