Identifying Antique Jewelry: What Does a 'Q' Mark on Gold Mean?

Question
I'm looking at purchasing an antique pearl brooch surrounded in an oval ivy/leaf setting in a "tested" 18k gold.  the only mark is the letter "q' either surrounded by brackets; "<q>" or the letter enclosed in a diamond shape that wasn't completly inpressed upon marking.  Any clue to the "q"?  No other marks exist!  Perhaps it could be an "a" with a long tail?

Answer
Hello Rod and thank you for your inquiry.  The only mark I can find in my resources is a capital "Q" inside a diamond shape.  It was the mark of The Barber Jlry. Mfg. Co. in New York City. They were in business 1922 - 1931 and did use gold in ring, lavallieres and other precious stone jewelry. Hope this helps and enjoy your jewelry !

Sally
jarrettsjade.com