Found on eBay. Came from the estate of COMMANDER PHILIP K. SHERMAN.
Not sure which USS Helena OR if the Commander served on the CL-50 or CA-75. (See update comments below the second picture)
He may just have been a collector of Navy memorabilia.

Permission to post this image given by Bob Martenis.
To see his other items for auction click HERE.

Shipmate Warren Peverill, A Division USS Helena CA-75, says the proof is in the paint.
Warren won the ash tray on an eBay auction in September 2007.
When it arrived at his home he noted a small spot of blue/green paint on the back of the tray.
He remembers this color as the same paint used on the CA-75 wardroom bulkheads when he served on the Helena.