If you REALLY want to go "big" in a Ruger No 1, check out Gary Reeder's website , reedercustomguns.com. He has developed 583 and 61o caliber "wildcats" for the No 1, based on the 577 Snider case. They push 550 grain hard cast gas check projectiles out at a bit under 2000 fps. Mr Reeder would be the most prolific wildcat cartridge/rifle/handgun builder today.
I don't know if you are still looking but have 416 rigby with 1300 bullets, 110 new brass and 40 loaded and 10 looked like once fired, but I believe not out of this gun I believe its unified. If interested in all am willing to negotiate a price for all.
To the contrary, @c bradley that gun has been circulating for awhile and I saw it a few years ago offered by an estate for sale. The gun was heavily used and then reworked extensively in the modern era. The modern/contemporary rose and yellow gold inlay work happened much later in the gun's life. It may not have even been a 500x3" NE when originally made. If you look closely at the gun you can see the voids and scuffs in the metal that are evidence of its long service life before it was fully polished, engraved, and blued in a modern style.