They're impressive looking instruments but Signature Analysis is dead except for a very few legacy systems that had SA capabilities and the meter functions can be replaced with a cheap Chinese made meter today. So there is no really good case for using a 5004 or 5005 IMO. I have a 5005 and I think a 5004 but I haven't used either one in over 10 years. Since I retired I've been collecting some very old TE, such as my HP 8405A Vector Voltmeter, and repairing it just for the hell of it but I doubt any of it will ever be useful again.