Looking for specific recs?

I've already heard of Kate Morton, Lucinda Riley, Barbara Erskine, and Susanna Kearsley. I love books set in dual or multiple time periods, with family secrets, hidden pasts, or time travel...also looking books about librarians, art historians, archivists, art restorers...books about even regular people discovering old objects: photos, film, a book, letters, mementos, art...discovering the history or story behind it? Like People of the Book or That Summer by Lauren Willig? Like books about someone that finds old letters from WWII by their grandma, similar stuff like that? THE OLDER OR OBSCURER THE BETTER! send me lots!

Possession by A S Byatt - dual time periods linked by documents

The Daughter of Time by Josephine Tey - getting behind a painting to a historical mystery

Cloud Atlas by David Mitchell - multiple time periods

Bless This House by Norah Lofts
Below the Salt by Thomas Costain
Doomsday Book by Connie Willis

Blue Skies has family secrets and time travel, and the main female character is a historic preservationist. It's free on Kindle right now.

Here a few, don't match all your criteria but you may like them:

A Cottage By the Sea by Ciji Ware

Reflections in the Nile by Suzanne Frank - more than one in the series

deeds not words by Katharine D'Souza about a woman who works in a regional museum, who uncovers secrets about her great aunt as a suffragette and a whole side of the family she never knew

A bit of an odd one - Strange Objects about a teenager on the West coast of Australia who discovers some items from the wreck of the Batavia in a cave.