I think you will like the 301. Nice that it is in a cabinet. Hopefully, it has the cradle and not altered like the one I got. It was in a Kenmore cabinet and to make it work, they took a hacksaw to the cradle, and I don't remember what to the cabinet. Fortunately, I have a card table that it fits in, if need be.
The difference between the 301 and the 301A is when they were made. Two of the pages on the site Mickey2 pointed to are
http://www.singer301.com/about/default.html and
http://www.singer301.com/dating/default.html The first is a rather long read, but fun information. The second is rather long, too. It tells why in 1953 they started putting the A on machines. From my understanding the Anderson plant was specifically for the new line of slant shank machines.
I really like the slant shank machines, except for sewing buttons on. I'm not sure why as I have been sewing buttons on by machine most of my adult life. But when I tried (yes, with the correct foot) it just didn't look as nice nor was it as easy as with a low shank machine.
Janey - Neat people never make the exciting discoveries I do.