I haven't had a chance yet to call the Department of Foreign Affairs yet (their office hours are the same as mine!), but I will, whenever I next get a day off, but have found a little more information on the jewels which were said to have been taken to Ireland.
My source on this occasion was 'Harry Boland, A Man Divided' by Andrew Brasier & John Kelly, which I quote below;
In the meantime, in the spring of 1920, de Valera and Harry would enter into negotiations with the Russian Bolshevik Government in Washington as part of their campaign to win recognition of the Irish Republic. In these talk Harry, without consulting anyone, would be given jewels to the value of $20,000 as guarantee against a loan the Russian's were seeking from the Irish Republic.
Pg 107
Harry brought the jewels back to Ireland when he returned, leaving them in his mother's care. When Harry died his sister Kathleen looked after the jewels before finally handing them over to the de Valera Government in 1932.
Pg 107
Years later Lavelle said de Valera told her when Harry had come home he brought the jewels to Collins, then the Minister for Finance and got a receipt for them. “Shortly afterwards, I suppose when the split came, Michael Collins threw the jewels back to Harry Boland, saying; ‘Take you d..n jewels’, forgetting that Harry still, had his receipts for accepting safe custody of the jewels. The jewels were lovely, diamonds and topaz mounted on platinum. When de Valera was returned to power in 1932 the jewels were handed to him and a receipt for them was signed by him” (Note 11, Page 198, James O’Meara). In 1950 the Irish Press reported that the Russian Government paid $20,000 to reclaim the jewels.
Pg 108
I believe that the source quoted above (Note 11, Page 198, James O'Meara) refers to a book listed in the bibliography called 'A Staunch Sinn Feiner' by Patricia Lavelle & James O'Meara
Some of the information in this book conflicts with that in 'Harry Boland's Irish Revolution', like the loan amount and the location of the exchange, but it does provide a little more information about the jewels themselves.