Someone who is not an active player, but is entrusted by the original poster (OP) with the exact event (by PM or email).
In the case of AlanK's CXXIII (123), the location can be found & demonstrated - but many events have occurred here over the years. Nobel Prize? Can't find one. AC-powered Machinery? I'm sure AlanK has something in mind. A banker would be the arbitrator for the correct answer. The Aviator's Chapel at the Mission Inn in Riverside was an example of place, not event. I really didn't have a specific event in mind, thinking finding the place was sufficient. In the case of the Cat & Rat mummified in the pipe organ, the specific event that I had in mind was the quotation by Joyce in "Finnegans Wake" - that was found with amazing speed.
Verum audaces non gerunt indusia alba. - Ipsi dixit MCMLXXII