This time it's Cursed by a Fortune, from 1897, written by G. Manville Fenn. This book has a striking cover image of a woman in a window, overlaid by a sealed will, together with a large English pound sign - all pertaining to the story within. It's a very Victorian tale of a girl who loses her father and inherits a large fortune, surrounded by guardians and relatives intent on obtaining her money through marriage. She is spirited away and kept under lock and key, but of course in the end it all comes right and she marries the poor doctor who loves her. Then she loses the fortune and everyone is happy. Except the bad guys, who are left in broken health to regret their actions.
There is no seahorse emblem on the cover, which makes me suspect this may be a slightly later printing of the book. It still uses gilt stamping and a gilt top to the pages, so it hasn't been drastically changed.