This one caught my eye over at Mike's. I contacted the original poster, and this is his description:
The conductors vary in size. There are a ton of branch circuits. I haven't measured yet, but I'd guess most of the branch circuits to be 14 gauge. There are larger conductors also.
The original installation included a larger conductor feeding from a distribution point out to a wooden splice box. the box had an asbestos backing in it. The conduits were all drilled through the back. The larger conductors were apparently daisychained to the smaller conductors that in return branched out to devices.
At a later date, somebody came back and installed fuse or circuit breaker panels adjacent to the various locations of the wooden boxes.
The raceway is constructed of a black cardboard like material on the inside and a very thin copper colored tin on the outside. Additionally, a seperate raceway is installed for each conductor.
The conductors are insulated with a woven material. Oh, and yea, you are correct, the inner insulation is rubber that crumbles to the touch....
A photo of the asbestos backed wood box showed screw holes and wire positioning that, to my eye, looked correct for this to have been a panelboard comprised of porcelain fuse blocks tapped off the larger conductors used as the bus.