A lesson I learned about 25 years ago.... If you can't sell it to someone else, always get a deposit. Most engravers don't have the self confidence to do this. They are afraid they will lose the job asking for a deposit. I never ask for less than 50%, and almost never lose a sale because of the deposit requirement. Very few people will walk away from a job if they have paid something up front, even if it is only $5. Remember, their time and money is valuable, even if they don't think yours is! In my later years, I even went to 100% deposits on smaller jobs with very little complaints. Most americans are used to paying in advance.
Mark