Read this article:
http://www.sqlteam.com/article/custom-auto-generated-sequences-with-sql-server[
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Concentrate on option 2 (Make it a presentation issue)...
All the difference between your line of identifiers between a identity field is the preceding E letter and the fact that you pad your number with leading zeroes to a fixed length...
That's only a visual representation and not really add to the uniqueness of the number - it means that if you remove those parts (E and leading zeroes) you still have a unique number...
My suggestion is to go with such a solution - use identity column and format it when presenting to end user...