In a college Algebra text, a problem shows amounts with the Euro sign before the amount. The 2007 EBAE updates added a symbol for the Euro which is 4, 15. This is the same as the Nemeth notation for Membership. The Nemeth Code was not updated to show the Euro as far as I know.
What do I need to put on the Special Symbols page, if anything? (The Membership notation is not used in this volume.)
Good question. Context and spacing will make it clear which symbol (4, 15) represents, and no rules say that we must list or define the Euro symbol, or --for that matter-- any other symbol that the Nemeth code shares with other codes. However, you certainly can use your judgment here: If the Euro symbol appears rarely in this transcription, you may insert a transcriber's note at that location, defining the symbol. If the Euro symbol appears throughout the volume, although EBAE does not include the Euro as a symbol required to be listed and defined on the Special Symbols page, there is no harm done if you want to list it.