Most stores in the USA seem to carry 3 types of cream these days:

Half and Half - usually 12-18% butterfat.

Table Cream - Can range from 20-30% butterfat. I've got a lot of candy recipes that call for 22% cream.

Heavy Cream - Generally 30% or more butterfat, around here it's usually 38%

As I recall, it takes about 30% butterfat in order to make whipped cream, so table cream generally won't whip into whipped cream. (McGee confirms the 30% figure.)

Corrected: According to McGee it takes about 25% butterfat in order for it to be stable, ie, adding cream to a hot sauce or soup without it curdling, so most brands of half and half are likely to break if used in a sauce.

In England you can sometimes buy double cream, which is somewhere around 55-60% butterfat. I've never seen it in the USA, not even through restaurant suppliers.

When I was growing up, our milk wasn't always homogenized, so occasionally there'd be a layer of cream at the top. That was pretty rich cream.

In most parts of the country, you can't buy raw milk in stores, though I've been told that in Nebraska if you go straight to the farm they can sell it to you, though the two dairy farms I've asked about it won't do it. I can get raw goats milk from a local goat farmer/cheesemaker that way, but have never done it.

The Wikipedia article on whipped cream says it takes 35% butterfat for cream to be whippable, but Harold McGee says 30%. The higher the butterfat content, the easier it will whip. Heavy cream is one of those things where I read the label carefully in the store, not all brands have the same butterfat content.

Having the cream and utensils very cold helps, some sources suggest putting the mixing bowl in the freezer for a half hour.

McGee also notes that 'natural' cream, that which rises to the top of whole milk, is only about 20% butterfat, the invention of centrifugal separators made it much easier for dairies to produce heavy cream.

I wonder if what you saw was Devonshire clotted cream?

I've only had it on scones and similar products, it's so expensive we don't buy it often.

My wife's scones recipe is sweeter than most, almost like a shortbread, except that it rises a lot. (Sorry, I can't post the recipe, she got it from a caterer years ago on the condition that she not give it to anyone else.)

Butterfat is the fat in the milk, so the nutrition label should have that information.

However, I generally won't buy a brand of cream if the carton doesn't explicitly list the buttefat content without having to search for it. That's just bad marketing on the part of the dairy.

There's something messed up about the product label in the link you provided. It says 'serving size 1 cup 240 ml' and says there are 16 servings per container. I really doubt that there are 16 CUPS in the package, that'd be a gallon container! Does the nutrition label on the package you bought say the same thing?

I can't compute the percentage of butterfat from the nutrition label because mL is a volume measurement, not a weight measurement, but if it is 5 grams of fat per tablespoon, the roundoff error (5 grams means somewhere between 4.50 and 5.49 grams per tablespoon) is so large that the calculation would probably be meaningless anyway. (That's one of the reasons I truly hate the mandated 'nutrition information' labels!)

If it says it is whipping cream, it has to be at least 30% butterfat to whip, so it's probably in the 35-39% range. I also found a contact page for Land O'Lakes, I'll let everyone know if I get a response to my inquiry. (In the interests of full disclosure I identified myself as a food blogger and mentioned that I intended to publish their response.)

Here's what another writer came up with: butterfat content of cream I doubt it is exactly 42% butterfat as computed on that site, but that's within the roundoff error range.