Some insurers attach endorsements to property insurance policies in which
all property damage (PD) is "deemed" to have occurred at a specific moment in time.
For example, the endorsement may provide that all covered PD is
deemed to have occurred at the moment damage first began, regardless of when
it was discovered. Under these types of endorsements, informally referred to
by some as "deemers," the insured's knowledge of a claim is not relevant to
which policy is triggered. As with the "first knowledge" endorsement, a given loss
can trigger only one policy (assuming all the affected policies
have this type of provision), but the actual policy that is triggered could
be different under these two approaches.