As far as I know there is only one type. There was a gold version years ago.
I have had 3 over the years and 3 avanti pro models there all the same mechanically just cosmetic differences.
Had a quick look their website and the picture on the page for a sheffield with an item number of 20504 still has S1002 stamped on the back of it and seems to have the same spec.
There was another special edition Sheffield which went by another name. It looked like a Sheffield but was made from magnesium called a Martin Bowler. I never had one but I think tigger did at one time.
Thought i had found an Okuma sheffield today in the Cash Converters shop nice clean box marked up £55.00 to finf someone has helped themselvs to the reel and put the empty box back bloke in the shop was well peaved ..