What RGB values are sepia

The RGB value for sepia is 112, 66, 20 (#704214).

The effect that you have in your old photo looks like a sepia toning effect on a cream paper or on a photo that had aged badly. Newly sepia toned images are usually whiter in the highlights as it's only the black metallic silver that gets transformed to silver sulphide during the toning process. Silver sulphide (Ag2S) is more stable than metallic silver and the toning was often done for archival reasons as well as aesthetics. The amount of the sepia toning can be varied by the time that the print is left in the toning bath.

Here's a scan of a genuine sepia toned print from the 1920s (my mother is the little bridesmaid crouching in the middle of the front row and my great grandmother is standing immediately behind her).