There is no clear separation between noise and signal. pfam00053 is very similar, but has 8 instead of 6 conserved cysteines. Includes some cytokine receptors. The EGF domain misses the N-terminus regions of the Ca2+ binding EGF domains (this is the main reason of discrepancy between swiss-prot domain start/end and Pfam). The family is hard to model due to many similar but different sub-types of EGF domains. Pfam certainly misses a number of EGF domains.