Carlos just sent me an excellent article by Marius Clore, published this year. It presents a highly-accurate method to calculate the expected molar extinction coefficients of proteins on the basis of the type and number of amino acids present, at a wavelength of 205 nm.
I have not only attached the Clore paper, but also the analysis of stathmin.
Punchline: epsilon_205 = 480480 M^-1 cm^-1.
Now... we have to find a UV/Vis spectrophotometer capable of transmitting and detecting 205 nm light. (I've asked Phil).