Sounds like he's referring to a 20275 diaphragm.

That's the early style, edge wound aluminum voice coil, 16 ohm diaphragm used in 604B,C,D, & E, 605A, 615A, B, 802B, C, and early D's.

The lit doesn't specify which have aluminum coils, i just know the 20275 does from experience. It's debatable how many healthy examples still exist. No doubt there are some, but they really need to be swept to determine that.

http://www.vintagewindings.com/gen%2...a-VocCoils.pdf