I forgot about the 1000 that thing was a monster, I have seen picture of it in comparsion to 200 size reels and it was big. I also think that I got it wrong on the 10ex, I think looking at the link Fish Tank provided it was just the model 10.
Phoneman what you are asking about is the progression of models over the years, there have been several. The B series I believe introduced the Chronarch and the Super Free Models SF) I believe the Citica was also introduced at this time. There was no C models, The D model came next and was a hefty jump in price over the B, ticked a lot of people off, but it was much more like the reels we use today, a true workhorse of a reel, built with a lot quality. The E series came next and many think that the Curado E may be the best reel of that model they have produced to date. At some point 50 series reels were introduced the MG stands for magnesium frame, the DSV just means it is a D model Salt Water safe version of the reel, the FV indicated Flipping Version. The 50, 100, 200 and 300 are what is used to identify to some degree the size of the reel but more so the spool size. They have also used the letter H to identify high speed reels, and well as the number 7 as in Core MG7.
So a reel like a Shimano Core 100MGFV would be a 100 sized spool/reel made of magnesium in a flipping version, and a reel like the 200DHSV would indicate a 200 sized reel/spool, D series, high speed, saltwater safe version.
Just a quick down and dirty and other can fill in the many holes I have left.