Need a lock

For a handle set, the best place to start is to measure the hole spacing (or the distance between the center of each mounting hole). I see you were viewing the 82-081; this handle set has a hole spacing of 4-15/16". If you're looking for the mortise lock in the door that the handle set interacts with though, honestly the easiest thing to do is to send us a photo of the hardware. From there I should be able to narrow this down for you.