Potential Mezzotint?

Prints are very difficult to identify by photos. It's best done in person. With a magnifying glass/loupe you can do it. Once you figure it out, it'll be easy to get a general idea of value. Here's a guide to identify the type of print you have:

https://pookandpook.com/how-to-identify-works-on-paper/

Here's a little blurb on the gentleman pictured:

https://en.m.wikipedia.org/wiki/William_Best,_1st_Baron_Wynford