It is finish coat which is made out of silver sand (finest sand) and lime. The finish coat does look smooth with a fine texture.
Sand cement lime render are not common to use because lime and cement are totally different elements.
If you use sand cement lime render it will kill the purpose of the lime which is breathable.
To make the lime hydrate into a lime putty, it must be soaked in clean water for at least 24 hours. Theputty can then be mixed with an aggregate in a 1:3 lime:aggregate ratio.
Putty lime is best to use to make a smooth mortar to apply easily.
There are 3 coat of lime and each coat has different ratio.
There are few kinds of render top coats such K-Rend, Weber, Parex these are premixed and coloured renders. Also there are other top coat renders such as sand & cement, lime render as well.
NHL mortars are today is primarily used in the conservation of buildings originally built using NHL mortars, but may be used as an alternative to ordinary portland cement. It is made principally of lime (hydraulic, or non hydraulic), water and an aggregate such as sand.