Like this old chap his suit has been around a long time,you don't see many flyless trousers in the 1870's which is when this was taken.His beard called a Newgate Frill was popular in the 50's & 60's with a lot of older men keeping them all their lives.
She's a bit more up to date in pretty much standard 1870's wear.The cardstock with rounded corners means 1875 is the earliest date & probably no later than 1880.
jim