This magnification visor provides both hands free for chart work, mechanical watch repair, and slide rule calculations. Link:
https://www.ebay.com/itm/334368400401?hash=item4dd9e8e411:g:B~oAAOSwsNhfB2jg&amdata=enc%3AAQAIAAAA8A6Do5M29frhrStCgEJ3vDZ7CIdB2B1M8YD4yBIjJqmGZPPmf6A7hlWW%2BWinwr6YrovgHyfyPRW7ilBJKDhfAYvfNiaSo27wQs7OQwHrCHiEkDsWgJcYy7ZPAHjrR4b1XKhB1AdsSRCbwDX0iAmzPgOMOKeXORgxFnRBaGqRxIhUKiYHSWQg594A8LS2U49ao9rePCA66oK85GEjkAjaEH8XUJYLlX7Mm0CymzHTRnuou0OfB9fMJCRqUrdnmEA6%2F64Nmux%2BsZQVp14puXuCyxr3SsSj6isT7VsUnzOKji7rJ5t9rY%2BUAkiJa%2Be%2Bg0ZoEQ%3D%3D%7Ctkp%3ABFBMwNmutqtj
