How does an amateur tell?

[General Butler]

So I have what looks.to be 4 nice sketches of prison life for Union soldiers on paper slightly larger then a postcard.
How can i tell if they are period or simply.copies of real ones or simply sketches done 5 years ago??.

 

[mofederal]

Have you seen the sketches anywhere else. Do they have age wear, paper aged or brown. They could be modern pencil sketches on period paper, it has been done, but not the easiest to accomplish. What did period post cards look like, or did they exist then. These are the simple things to ask and check around about.