Hi David,
I show Sylvia Lockwood (b Lyndon abt 1824) marrying Nathaniel Briggs on 27 Jun 1840 in Lyndon, Cattaraugus,NY. Her parents were John L Lockwood and Roxanna Sherlock. My source is a letter written 8 Jun 1977 by a Joseph P Sloan of Brockway, PA.
I'm in Maine at the moment so don't have access to my paper files, etc.
I'll be back in NY in a week or so.
Email address is sidk8zes#wildblue.net (sub @ for#)
Regards, Sid Emmons, Historian, Town of Lyndon