Letters from cricket legends WG Grace and Ivo Bligh are being auctioned to raise money for a new cricket museum in Cardiff.
The museum at the Swalec Stadium will tell the 122-year history of Glamorgan County Cricket Club.
"The letters are truly unique," said Richard Madley of auctioneers Dreweatts.
Other lots include a set of Wisden Cricket Almanacs from 1864 to 1970, which could raise £2,000-3,000 each.
It is hoped the auction will raise a total of £100,000 to help fund the museum.
Mr Madley said the collection of items to be auctioned would give an insight into the history of Welsh cricket.
Grace, who died in 1915, was a colossus in the English game whose first class career spanned for 43 years, while Bligh is remembered as the England captain who won the original Ashes in 1882/83.
"Just their signatures could sell for several hundreds of pounds on their own, but the story they tell of Glamorgan's early cricket development is priceless," said Mr Madley.
"Ivo Bligh is quite disparaging about the standard of cricket in Wales, and appears reluctant to travel here.
"He describes the late 19th Century Glamorgan side as 'third rate', and 'amongst the worst of the minor counties sides'.
"WG, on the other hand, seems a lot more supportive.
"He writes in 1891, just three years after Glamorgan were founded, to offer a game against his Gloucestershire team.
"Mind you, that could be to do with WG's famous interest in his own batting average, as he offers to bring a weakened side to Wales in order to make a game of it - so he can't have thought that much of Glamorgan's ability either."
Serious collectors will also be interested in the set of Wisden Cricket Almanacs.
"I would say that the Wisdens are so valuable because of their rarity, but that's only part of the story," said Mr Madley.
"The truth is that Wisden's headquarters were bombed during World War II, and all the original records were lost.
"So nobody has any certain idea of how many early Wisdens were printed in the first place, let alone how many are left today."
The planned cricket museum is the final part of the Swalec Stadium's £9.5m transformation into a 21st Century arena with state-of-the-art playing facilities and seating for 16,000.
Last summer it held the first Test match in Wales, when England drew against Australia in the opening game of the Ashes series.
The idea for the auction came about when staff at the club began planning the layout of the museum, and realised how many exhibits they would never be able to display.
Glamorgan chairman Paul Russell said: "This is an important sale for the club, although I have to stress we are not selling off the family silver.
"The items going to auction are those that have been gathering dust over the years, we feel we can live without and which would not be housed in our museum."
An auction of modern lots took place last week.
Older items, which will also include an autographed portrait of the oldest man to score a Test century, Sir Jack Hobbs, will go under the hammer in a sale conducted by Dreweatts at Bloomsbury Auctions in Mayfair, London, on Thursday, 10 June.