I use to follow these very closely and have to admit that I have never seen one. That isn't to say that one did not exist and they may have issued a special one. Just saying that I have never seen one but have seen other makes. ....
If you have one or know of one, then it should clearly be marked as being a Savage 311??
I just purchased one that has a bright nickel finish on the frame, but I do not know if it is factory. I tried to contact Savage and I got directed to contact some guy that doesn;t even work for them.
When the case colors get "disappeared" from the action of a vintage American SxS, the basic Chromax receiver material appears as a shiney, chrome-like finish.
I don't believe they made a 311 in nickel or chrome. Otoh, their similar Fox Model B SxS was sold for a time with a satin chrome receiver, so anything is possible.