This is a very valuable first edition book by Clarence Hailey from the early 20th century. The title Thoroughbred Sires is only in three libraries Worldwide and is seen on the Worldwide markets but not often. This collection taken from pictures by this known author on horses from the period, contains, as you note, 100 engravings of "thoroughbred sires; with their tabulated pedigrees (at end of book)"
Currently you can find some trying to get more for the edition but the true market value of the book is in the range of 500.00-600.00 (USD) when you consider past sales of similar items documenting horses from the last three years as well as high end auction sales of similar material in recent auctions.
Here is one record from New Zealand but I was unable to find what it sold for - I believe it is a bit low in the estimate looking at the market and how many are out there. This shows to that it is not completely rare but scarce which is good to keep in mind.
Lot 206: [ Books ]
Hailey, Clarence. thoroughbred Sires the Collection contains 100 engravings of Thoroughbred Sires, with their Tabulated Pedigrees (at end of book), 1st Ed, Clarence hailey, Newmarket, 1908, full green morocco gilt, covers worn and marked, FX, else G.
Dunbar Sloane: Wellington, New Zealand
Auction Date: September 30, 2009
NZD300 - NZD500
All my best, Dori