Help ID Bird Prints

Bought 3 Prints (or maybe originals?) today and am totally confused by the signatures. Each print has a small scrawled signature right under it that says something "Clark" and then a year (see pics), but then each print has a sentence on the border that says "Hand Painted by Radcliffe". The something "Clark" looks printed, but the "Hand Painted by Racliffe" is written in pen...looks to be added later. Did someone find uncolored prints by this "Clark" and then paint them in signing "Hand Painted by Radcliffe"?
I am totally at a loss...Very confused, haha.

It looks as though an amateur artist, Radcliffe, has hand coloured a number of black & white illustrations by an artist called Clark.
Have the prints come out out a book? If so, you might be able to find the illustrator, Clark, on Amazon or ABEBooks, but there are no listings for an artist named Radcliffe, so he/she may originally have been the book's owner (my mother used to do the same thing when she was a teenager).

hmm, interesting, thank you. I'm not sure if they came from a book, when I bought them they were just individual sheets.

Book illustrations used to be printed on separate (& smaller) pages from the text, and then glued along the top margin to blank pages in the book, with a page of tissue paper on top to protect it. When removed these illustrations can look like seperate sheets of paper or card.

I see in my original post I forgot to post the sheet sizes...They are quite big at 22" by 28". At that size, could they still be illustrations from a big book?