Tolman and Etherington

In working on the More paper, I found myself looking through cosmography literature from 1929 through 1933. There is a series of papers by Tolman, in which he works out the Tolman test for the expansion of the Universe, which I think of as being a test of transparency and Lorentz invariance. Tolman worked out the test in the context of one world model (de Sitter's); his interest was in understanding the possible physics underlying the steady-state model; Etherington generalized it to a wider range of world models in 1933. After Etherington's generalization, the community should have realized that the test doesn't really test expansion per se, but it does test relativity and electromagnetism in that context.