The model 6 p/n 560 is actually made under license by Sekonic, neither Weston nor Sangamo, 'tis said. Mine came with the optional Adams Zone dial, which is why I bought it out of interest.
Took me a while to figure out the Adams Zones bit. There's a small arrow where "V" should be. Basically, it gets pointed to the meter reading on the inner dial by rotating the outer dial. Pick the desirable resulting aperture/shutter combo and the metered object will render as middle luminance i.e. the object will be "placed" in Zone V. To place the object, e.g. snow, in a lighter Zone, rotate the outer dial until perhaps "VII" is pointing at the meter reading ... or, for a coal heap, rotate the outer dial until "II" is pointing at the meter reading. These additional rotations change the exposure appropriately and are equivalent to Exposure Compensation now that the Zone System is almost forgotten.
To test the degree of compensation for snow, I figured the Exposure Value recommended by the illustration above - it is 13 Ev. (from log2(N^2 / t).
Then I turned the outer dial to align "VII" with the same meter reading on the inner dial - sure enough, the recommended Exposure Value changed to 11 Ev ipso fatso.
