  Classical sequential growth models for causal sets provide an important step
towards the formulation of a quantum causal set dynamics. The covariant
observables in a class of these models known as generalised percolation have
been completely characterised in terms of physically well-defined ``stem sets''
and yield an insight into the nature of observables in quantum causal set
cosmology. We discuss a recent extension of generalised percolation and show
that the characterisation of covariant observables in terms of stem sets is
also complete in this extension.
