Hi Alpharalpha,
A Dunlop latex at 5.6 lb. would be about a 90 kgM3, which converts roughly to an upper 30 / lower 40 ILD. Most manufacturers would consider this density most appropriate for a support core or a transition layer in a firmer mattress.
Talalay is normally classified by ILD, whether or not it is blended. Dunlop latex is classified usually either by density or ILD.
It’s important to realize that there is no such thing as a “single number ILD” for any Dunlop core that will be accurate and manufacturers list an ILD or even a range as a convenience to make approximate comparisons. This is also true to a smaller degree with Talalay although in practical terms it is much more consistent even though it is also “averaged” (in the case of blended Talalay). Even if the ILD is measured and “averaged” across the layer … it will vary by individual layer and will also vary depending on whether you have the bottom half or the top half of an original Dunlop core that produced the rating. The top 3" of a molded 6" Dunlop core will generally be softer than the bottom 3". It can also vary depending on which side of a layer you are measuring.
Dunlop and Talalay aren’t directly comparable in terms of firmness using only ILD numbers because there are several factors that can affect how soft or firm a mattress (or an individual layer) feels besides just the ILD of the material (see post #4 here) and Dunlop and Talalay that are the same thickness and ILD won’t feel the same in terms of their firmness for most people because they have a different response curve and compression modulus (how quickly a material becomes firmer as you sink into it more deeply). There is more about the difference between Dunlop and Talalay in post #7 here.
You can scroll down the list of the different mattress cover vendors in the component post here. Some will have wool quilted in the cover (which is excellent at temperature and humidity regulation) and some will offer stretch-knit covers with nothing quilted to it.
Phoenix