Antique Amethyst & Diamond Stickpin - Potential Value?

Question
I like old jewelry so I shop yardsales and flea markets.  About 2 weekends ago I purchased this beautiful stickpin for fifty cents.  I have a jut feeling that is worth a lot more. It is about 3 to 4 inches in lenght with a large round smooth amethyst stone which is beveled and headed with a single stone which I am almost 100 percent sure is a diamond which is round cut. On the back it is dated july 17 1917 with an upsided down three leaf clover with the number l in the left leaf and the number 4 in the right leaf and there is a small A+ under the 4. I would like to know more about the mark and date and also the piece itself. I couldn't be a birth date because purple or amethyst is not the stone for july.  As far as monetary value do you have any idea.  It is a beautiful piece to me.  Thank you

Answer
Hello Joyce and thank you for your inquiry. Unfortunetly I haven't been able to locate a manufacturer with that specific marking. My advice would be to have it checked by an estate jewelry appraiser or gemologist to determine the value of the metal and stones. The letters might hold some significance as to the type of metal - possibly European. The type of metal and stones would also be a determining factor in the value. Hope this helps and good luck.