Hi jcolm - "PRS Electric" does indeed indicate an earlier CE model - but I have seen that logo on some early 1991 models - so it's not a guarantee of year. Get the serial number and run it here
http://www.prsguitars.com/csc/year.html. Bolt-on necks are easy to swap
Body wood should be alder up until 1995 or so. All-alder models (no maple top) are 2-piece, while maple-topped alder models are 3-piece. If the back is opaque you can usually see the seams - if its not you can sometimes see the seam if you hold it up to the light. Mahogany models have a one-piece back.
RE: rotary vs. 3-way (McCarty) switching - I have not seen any documentation indicating a specific year correlation - all of my CEs are rotary-equipped. It's also an easy conversion from rotary to 3-way, and many folks prefer that setup, so this would not be a good indicator of year anyway.
Happy shopping - the good news is that there ARE no bad CEs...just well-loved ones...they are fantastic guitars.