The Classic works with any metal wand PN, all the way back to the first electric hose on the 1205, though there are probably some variations in the early years with the PN cord connection on the wand. I can't recall if they all used the same plug from the PN to the hose or if the early electric hoses had a different connection.
The connection absolutely is the same from the Silverado Deluxe to present day. It was probably the same several machines before that, but I feel like my old 1205 had a funny plug at the wand.
The Legacy works with **most** plastic wand PNs. The Legacy was formerly known as the Epic 6000 (steel wands, not compatible unless a new hose is fitted), but the Epic 6500 introduced plastic wands. Also the Renaissance machines (including the Epic 8000, Guardian) used the same plastic wands and have a compatible PN.
The Guardian Ultra and Guardian Platinum machines are the most incompatible of the bunch. They use a unique plastic want shape that doesn't work with the long line of Epic/Legacy/Renaissance plastic wand systems and power nozzles.
I personally don't have a problem with the plastic wands. In some ways, I prefer them. When I use my Epic 6000 steel wand machine, I have to manually unplug the PN cord from the wand when I switch to the floor tool. With the plastic wands, the power is transmitted inside the wand, so all you have to do is disconnect the PN and snap the floor tool on. No cord to worry with. And I like that the plastic wands don't fall apart... we've all had a steel wand or accessory slide apart before.
That being said, Aerus is in dire need of an updated wand system. They need a modern steel telescoping wand that can work with the Classic, Legacy, and Platinum that doesn't have a dangling cord at the PN (like the old school steel wands) and that isn't plastic (like the Legacy and Platinum). But they also need to make the Legacy and Classic machines HEPA, considering the entry price, and I personally think the Legacy or a new 4th model could go cordless/battery electric. A Classic/Legacy-bodied machine running on battery power would be a major step forward for the brand.