"I recently cosigned a large piece of jewelry with Koop.  Justin was very knowledgeable about the value of the item and market pricing.  Justin is fantastic to work with and the piece I consigned sold quickly!  I highly recommend Koop for cosigning jewelry or any jewelry needs you may have.  Justin's professionalism and customer service is next to none!!  They are a five star business all the way!!"

"I don’t just like Koop Diamond Cutters, I LOVE them!! Quality jewelry and a friendly staff.  I adore the SPARKLES of my wedding set. Justin Koop helped me design a custom pendant for my mother, for her birthday, that she never takes off. I highly recommend you check them out for your next jewelry purchase."

"We have used them for many years. Nothing like them in the city!"

"Our family has been doing business with Koop Diamond Cutters, Inc. for over 32 years.  They make beautiful top quality jewelry!  Would not go any where else!!"

"1981 - I remember the look on Mom's face when she showed me her new investment...a 150 CT topaz. Being obsessed with gems and minerals from before I could read, I was completely mesmerized...and so sad that from that moment till now it never saw the light of day. Yes, it's monstrous so this sentimental project took architectural ingenuity. Justin mastered the piece honouring the stone, my style, and intent to wear often.  It was so much fun interacting with Justin and the end result is perfection.  I'm so glad I was referred to Koop DC!  Sincere thanks, Justin!

"They created a ring by incorporating my engagement diamond and 64 brilliant cut diamonds into a contemporary knock out ring for my 50th wedding anniversary!"