Pair of Antique Pastel Portraits

I found these two large pastel portraits at a yard sale about 18 years ago. They are unframed though each one has a wood box frame around it with the portrait attached to the back of it (it sets back so the pastel wouldn't touch glass I am guessing). They measure 16" wide X 20" high and as you can see portray a rather somber looking couple. They are really in absolutely beautiful condition. Neither piece is signed.
 
I am trying to determine the age of these portraits and hope someone might be able to identify the style of clothing or even a time frame when these may have been done. I was told at one time that they may have been done after the introduction of photography in the 1840's, as they seemed to to be photos colored with pastels to make them appear to be painted from life.
 
I haven't been able to find much information on how one would determine if that was in fact the case.
I have included a close-up of each one so you can see the pastel, and the backs of both. Again, any information that anyone might have to shed some light on these portraits would be greatly appreciated.