Are These Crayon 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 a time period and a farfetched fantasy that this is a known husband and wife.
 
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.

I think you could be looking at a slightly later date from the costume - 1860s. The ladys bonnet is a give away, the dropped shoulder with gathered detail and the higher waistline and the lapels on the mans frock coat. I also think they may actually be photographs underneath which someone at a later date has "coloured in". I have a few of this type of thing where charcoal or conte crayon has been used to accentuate the image and the subjects features. I'm also basing this on the fact these are very fine in their detailing and that  somebody has followed the outlines very well. By the 1860s larger portrait photography was possible alongside carte and cabinet de visite type prints, or they could have been blown up from negative glass slides at a later date. Hope this helps

Thank you so much for the information. It is very helpful. You said you thought there may actually be photos underneath and my understanding of Crayon Portraits are that they used some sort of solar enlarger to blow up negatives to a large size in order to do this. I also had some comments from another site where I posted these saying that they felt they were to perfect to be solar enlargements or crayon portraits are usually slightly off proportion-wise and these could possibly be actual pastel portraits. I love a mystery. Again, thank you for your time and help. I will use that in my research.