Establishing the nobiliary status of such families depends upon various factors and is essentially twofold. While most local officials or wealthy landholders could not claim nobility, the use of such titles does serve to support the possibility of nobility in some cases. Secondly, associated heraldic evidence must exist. The family must have been attributed a coat of arms that appertained to that family in particular, not to another in the same region which coincidentally bore the same surname. The coat of arms might be found as the engraving on an ancestral residence or the seal in a document.
Circumstantial evidence is important, but it can be misleading.
For example, one might conclude that local residents who share the surname of the local duke are his kin, and therefore nobles. Documentary research, however, might well demonstrate the contrary-for they might descend from the ducal family's servants. This was the case in the Sicilian town of Castelbuono, where dozens of families bore the surname Ventimiglia even though they had no kinship to the family of that name which resided in the local castle. Anecdotes are rarely accurate or demonstrable. A frequent story is that of an ancestor's having been the illegitimate child of a local nobleman.