What is the most successful company to only produce a single unique product? See OP for more info.

Good lord, they don’t even tell you what flavor of jam it is? Please, I have to know. . .

If we are allowing companies which no longer fit the bill, I’ll submit the M&M company before they bought Mars.

Also, the British Royal Family, which has produced “male heirs” exclusively for centuries. There was of course, the female line, largely considered industrial waste through most of history. It has nonetheless proven itself useful in the most recent model and was made an official first-line offering just a couple of years ago.

Otherwise, it’s probably the maker of some tiny auto part or other. It’ll be some little genius accessory or fuel efficiency booster which every car needs these days and is still under patent.

Even then, serial number or batch number would differ.

Would the OP please redefine the question before we try to anwser it, then get rebuked for doing so?

Well, there are plenty of actual food businesses that do just that. I don’t know if any do billions in sales but certainly millions and in operation for several decades. I can’t think of any big chains based around 1 product, but certainly locally famous and touristy places that do big sales and have long lines. I think different sizes might be a disqualifier, though now that I think about it. I supposed the kids lemonade would only be 1 size.

Already definitely refuted in my earlier post. They are getting into the synthetic diamond game (hardly equivalent products) as well as side businesses such a grading.

Reading through the reviews, it appears you can order the donuts without jam if you want, so depending on the strictness of the OP, that may qualify as a second product.

“Do you want that with hemophilia, or without?”

Some software firm is likely to be the best answer here, if De Beers is ruled out due to diamond variance.

I’ll guess Dropbox, which has exactly one product - and though there have existed prior versions of their product, only one ‘is their product’ and is supported at a given time, and updating to the current version is automatic and required to use.

Dropbox has a market cap of around 13B at the moment.

Don’t know if it meets the OP’s criteria since the original company/product was acquired(for $47. 5 million)back in 1974, but how about Liquid Paper?

From 1890 to 2003, there was one single product: Goldenberg’s Peanut Chews.

I was deeply hooked on them from about 9-15. They’re a unique flavor. And until some knuckle-headed candy company from down Lancaster way bought them up and fucked with the program and made " Milk Chocolatey" a flavor, ( what the hell is “Chocolatey” ??? ), it was a single formula and product.

Damned fine candy. And a nice family. I went to school with an heiress to the family company. She always came through at parties with a bunch of movie theater sized product !!!

They have at least three different plans, and probably many variations on the Enterprise plan.

Dropbox also makes Paper and used to make Mailbox and Carousel.

Many companies involved in gold mining and processing would be singular in mission.

Mine ore , crush ore > process ore chemically > (Au CN particles), filter AuCN out with carbon (AuCN+C), smelt that to get Au again, melt gold into bullion gold . The outputs are the same grade even if the input was weak or great.
This beats debeers, coal, electricity as they have defined grades that they do different things for. Coal comes in various grades, and they also have chitter (clay and carbon mixed… extremely high ash , as the measure of quality is ash level ) and overburden to sell. Coal mining companies typically then have land to subdivide and sell.

Another might be water… An owner of a dam may have one single product, eg the water that they sell varying amounts of, but its all the same … dam water + chlorine.
Or they sell the hydroelectric power, being from one generator, with one connection to grid… one product ?
But I assume gold mining co are larger than any water.