Store loyalty cards attached to a set of keys took investigators involved in the search for missing woman Elaine O'Hara to Vartry Reservoir, the Central Criminal Court heard.
Dunnes Stores was first to confirm to gardai that a serial number on a card recovered from the water in Co Wicklow on September 16, 2013, was registered to the 36-year-old who had vanished a year earlier.
It was another three weeks before the Garda water unit recovered a set of glasses in the almost dried up waterway, which investigations found had belonged to the childcare assistant.
Peter Curtis, of Specsavers in Dun Laoghaire, told the court an eight-digit serial number on the frame of the glasses, and the prescription on each lens, made them "unique" to one person. That was Ms O'Hara, who had been a customer since 1997.
Aidan Kelly, of Dunnes Stores, and Jean O'Donnell, of Applegreen, also confirmed serial numbers on two store cards attached to the key ring were registered to Ms O'Hara at the time of her disappearance.
All three gave evidence on the sixth day of the trial of Graham Dwyer. The 42-year-old architect, of Kerrymount Close, Foxrock, is pleading not guilty to the murder of Ms O'Hara, at Killakee, Rathfarnham on August 22, 2012.
Ms O'Hara, a childcare assistant from Killiney, was last seen alive near Shanganagh Cemetery in Shankill.
Her remains were found by a dog walker in undergrowth in the Dublin Mountains on September 13, 2013.
Engineer Eamon Fleming told the court water levels in Vartry Reservoir in August 2012 had been unusually high after the "wettest summer on record", but were unusually low in August 2013 after the driest summer since 1995.
He told prosecution barrister Anne Marie Lawlor that by that June the reservoir had started to dry up, and the level dropped rapidly through to October.
The court heard that on September 10 2013, angler William Fegan, his brother James and friend Mark Quinn spotted a rope and something shiny in the water below from the bridge near Roundwood.
With a tension strap and hook they tried to fish it out, but pulled out a dirty vest. Next came a rope, chains, handcuffs, a blindfold and a ball gag.
The next day Mr Fegan went to gardai and five days later more items were fetched by Garda James O'Donoghue, including the set of keys.
Once he knew they belonged to Ms O'Hara, gardai in Dundrum investigating her disappearance and officers probing the discovery of a body in the Dublin Mountains arrived.
By October 7, when the Garda water unit did a finger tip search of the muddy water bed, the list of exhibits being held in evidence bags has expanded to included several knives, cuffs and chains, a mobile phone, Sim cards, batteries, clothing, several sex toys and a leather bondage mask, with a zip over the mouth and each eye.
Other items "as diverse as" a mattress, a desktop computer, a Dire Straits CD, a small tub and a glass jar with liquid in it were also recovered, Garda driver Lorcan Byrne agreed under cross examination by defence counsel Remy Farrell SC.
The trial continues.