Lots of information on the different model types in this thread:

http://www.bikeforums.net/classic-vi...e-mercier.html

Lovely bicycle, anyway. Looks like it doesn't need anything other than a wax and polish. Mercier 300 would be my guess, the only difference I can see from the standard model is the lack of chrome socks, but maybe that depended on the year. I hope you're not planning to change to much on this one, looks perfect as is.