Thanks for your insights Tim! I actually have two of the old Jim Williams designed Rode NT2 but the Capsules are sitting in a draw after swapping them out for k47 types because they were way too bright for that circuit! I may have to revisit them by dropping them in an appropriate circuit(U-87-U-67 ...The version I have has an acrylic back-plate with some sort of metal or metalization on the face of the back-plate.These days with chinese K67 capsules it's hard to see the forest for the trees so I'd be hard pressed to pick one. It's not my favorite capsule. I mention the 797 Audio capsule because I know the Microtech Gefell engineer who helped them build their original model and their quality is very good.
Generally it's not the backplate that's wrong with these , it's the membrane tuning and rest of the capsule setup.