Addition to above post: The Rehearsal Marks were first entered as letters and later changed into numbers. I found out that only after deleting all letter-rehearsal marks in the score and entering numbered-rehearsal marks, all parts also show numbers. Question remains if there is a way to change rehearsal marks in score and parts without having to delete all exeisting rehearsal marks? Thanks!

In your expression palette, you can delete the "letter" expression from the rehearsal category. It will say that this expression is being used in this file and give you the option of choosing another expression to take its place. You choose the "number" expression from the rehearsal mark category to take its place.

By doing it this way you only have to delete this once and all occurences of this will be changed to numbers. I would make a copy of the score before doing this just in case something goes wrong.

Another way to do this is to the select all, go to the utilities menu, look for "change". Choose expression. Then select the letter expression and select the number expression to take its place. This method will keep the letter expression in the rehearsal category without deleting it.

@Jeffrey Turner: Thanks for your reply. Still seems odd to me that there is no direct, simple way to do this.