It's 5 years Alfa Tango implemented 5xxAT0 callsigns, and many AT members still have no clear idea about its use. They are used in ANY case the activator's SAFETY needs it. 5xxAT0 callsigns has NOTHING to do with other AT Rules regarding DX-pedition callsigns. ... ANY of the callsigns of the 5xx series, will be used for a SINGLE activity, it's a simple sequential number, having NOTHING to do with the QTH. Evaluation of requests are made ONLY by AT SuperCommittee. As per 2015 HQ decision, 5xxAT0 callsign released cannot be used to make advertising, request of sponsoring etc. Obviously, if activator asks HQ to help him, regarding safety issues, he must be crazy to advertise it openly! HQ decision is final. In NO way 5xxAT0 callsigns will be modified to let understand QTH. Sorry to repeat it, it's a SAFETY issue!