>>>Excuse me for asking a stupid question, but did you also SET CENTURY ON?
>>
>>set century to 19 rollover 60 implicitly sets century on.
>
>No, it does NOT.

You are right, my aplogies. However I confirmed that CENTURY is on. I think I found the problem. The legacy application that inserts the data does not have CENTURY on. Therefore, the index the index can't match my expression. If I reindex the table and try the same seek, everything works as expected.