Thanks - I did a search for those tonearms. This site: http://www.thevintageknob.org/SONY/sonyvault/PUA286237/PUA286237.html
leads me to think it's the PUA-286 - it looks as if that model has a cueing lever and the other does not. If you have a way of sharing the user's manual, that would be great, especially because when I tried to print the webpage above, I couldn't.
Many Thanks!!!