Hi Lesley...well, as photography wasn't even invented (practically speaking) until 1839 it was a thing of the future to George Sr.
The sitter's clothing is undateable really, but by the pose and backdrop and the style of the frame I'd say mid 1870s. I think I can see a headclamp stand behind him, to keep his head still, which pretty much disappeared by 1875 or so, but it isn't any earlier than this because of the frame.
Do you have the original, and did you scan it yourself? If so, I suggest you may have used the wrong scanner setting, which should be photo mode rather than anything else. You would get much better results were this scanned in photo mode.
Cheers,
China