Value of these Sheffield Candlesticks...with these marks?

I need some help with this…

I am trying to establish the value of these Sheffield Candlesticks that the owner insists are sterling silver, not plated. They have been passed down from her great grandparents.
How can I confirm that this is a hallmarked silver item vs. plated?
And what would be their estimated value?

The markings on each candlestick are: Makers initials: JKB/TH/GW; Marks for Sheffield Crown and Lion Passant; date letter D and monarch’s head facing left.
Each candlestick is Height: 7.5”; Weight: 1 lb 15 oz

Thanks
1-6.5.09 004.JPG
6.5.09 007-1.JPG
6.5.09 010-1.JPG

I can confirm that your picture shows a Sheffield hallmark for sterling silver with a date of 1871 and the maker’s mark of Hawksworth, Eyre & Co of Nursery Street, Sheffield. This mark was registered in November 1869. JKB, TH and GW were James Kebberling Bembridge,Thomas Hall & George Woodhouse. I hope that someone else will be able to give you a value.

Thank you so much for your response. That’s wonderful information.