The provenance would need to have some pretty solid evidence to affect the value.
Can Churchill verify the Eastman connection?
Remember, most fine rifles of the era were made for someone in particular - bespoke so to speak - and they were all “somebody’s” for the most part.
The ledgers from the big name makers read like a “who’s who” of industry and society.

That said, the big bore single shot market is a funny thing unto itself.
All of the things we see as attributes in a double, adding value, don’t always translate to single shots. Some do of course such as engraving over a plain example. Take downs are always popular and more lately, chamberings which are easy to source and easy on the shoulder (singles being lighter generally) make for an easier sale.
303s are pretty hot right now checking those two boxes in particular although the absolutely correct 215gr bullets of the day are a little scarce.
Average condition big bores seem to sit on the market (at retail) for quite a while. I know firsthand how that is having offered a couple of mine to later decide to keep them instead of sitting on the market.
Your rifle is better than average - average in a used Farquharson or other British falling block can be pretty rough actually.
Being a 470, this rifle is probably easier to feed than most other “big bores” other than maybe a 450-400 3” except that I would guess that only 500gr bullets are available which makes it a challenge to load down as one can with a 450. Full boat loads in any of these big singles wears thin pretty quickly.
470s are not common though as that chambering came in about the same time as the economical single shot rifle was overtaken by the availability of inexpensive, reliable bot actions.
Super cool rifle though, that’s for sure.
One I would like to have too!! LOL!