My source is -

Roberts, Hugh 2012 The Queen's Diamonds, London: Royal Collection Publications

"Attributed to Bolin, St Petersburg, c1874"

"...was made for the Grand Duchess Maria Pavlovna (1854-1920)...by the Russian court jeweller Bolin apparently at the time of her marriage in 1874."

"..was ingeniously smuggled out of Russia by her friend and confidant, Albert Henry (Bertie) Stopford..."

"...sold by the Grand Duchess's daughter, Princess Nicholas of Greece (1882-1957), to Queen Mary."

"The frame... was completely remade by Garrard in 1988."

My comments -

First, I am not aware of any more recent information.

Unfortunately, most material published by recognised authors or official sources has been proved to contain errors. This applies to The Queen's Diamonds and the many other books about royal jewellery. The website of the Royal Collection Trust has also included incorrect detail quite often which is very disappointing.
Broadly, I do not rely on blogs, websites, and social media featuring royal jewels, but especially when they do not cite their sources.

The Queen's Diamonds was a huge undertaking for the Diamond Jubilee of Queen Elizabeth II and Hugh Roberts is to be roundly commended for this work.

He must have had to rely on loads of information already compiled by many workers at the Royal Collection and I believe that is where some faulty work (I avoid saying research here) managed to be included.

As regards the website, I have often been appalled at some blunders.
However, I think today's priority is primarily to entertain and not to provide authentic information.

I do not believe we can ever again expect to see a thorough research project starting with the outstanding primary sources available to the Royal Collection.
The cost would be prohibitive.