Beautiful vintage Abraham David Loewenstark blue topaz and diamond ring. Hallmarked “10K” and “ADL”. Size 6 3/4. Just cleaned. Please see pictures for additional details. Abraham David Loewenstark was a master jeweler known for high-quality vintage and antique fine jewelry. His work is frequently identified by the hallmark "ADL", which is typically stamped alongside metal purity marks (such as 10K or 14K) on the interior of ring bands. I am a trusted seller and I ship fast.