Let me know if you figure it out. Had a similar situation with ATtiny45 and ATtiny85. Datasheet sez revisions are marked, darned if I could figure it out. I finally concluded, by running the same code on each and observing current consumption, that the t85 that I had did not have BOD disable implemented, but the t45 did.
I'd be a bit surprised if specific silicon revisions could be ordered via the usual channels, or if the distributors are even aware of the revision. They probably ship what they have, usually FIFO (more or less).