I believe I posted a little on this Gibbs when I bought it at auction some years ago.
Steve Bertram recently finished it and I got it in hand as soon as I could!

The rifle had been rebarreled to 7X57R iirc, and the forend had been replaced at that time.
The action was blacked but the stock and steel plates looked generally unmessed with.
Oddly and fortunately, the smith set the original rear sight leaves on the new barrel island.
Often Gibbs Sporters have the powder charge and bullet weight engraved on the sight as this one had. Some even had the charge and bullet weight for TWO different loadings - an express load and a load with a heavier bullet each shooting to the same point of aim!

The barrel we used is a Ron Snover Metford rifled barrel that I got off of a big Webley which had been barreled in the '80s or '90s as a long range match rifle chambered in 45-90.
That rifle was rebarreled by Steve as well in .500NE.
See here: http://forums.nitroexpress.com/showflat.php?Cat=0&Number=289147&an=0&page=1#Post289147

In the match configuration, the barrel had enough length to cut and chamber and enough weight to replicate the profile of an original 461 Gibbs sporter, which I happen to have.
The forend was also copied from my 461 and checkered by Steve Dalzell.

So, I had a Selous plated Gibbs action and stock, as well as a spare correctly rifled Metford barrel. The decision was obvious!

The only question for me was, which 450 to chamber this rifle in?

The barrel is a .458 so slightly smaller than the correct .461 Gibbs Metford barrels but, interestingly, some 461 Gibbs sporters - even one Selous himself owned - were stamped "450EX" so mine would be too.

I chose the 500/450 No.1 Express because it is very cool, of course, but also because I already had brass and dies as well as bullet swaging dies to make patched .458" bullets of any weight I desire. Being a former match rifle barrel, it has a fast twist so heavy bullets will stabilize nicely - Steve and I shot this with 480gr patched bullets during the build but I'd think that any from the 360gr on the sights to the full weight 570gr bullets will shoot satisfactorily.
We will have to see just how a 100/360 load shoots but honestly I hope that the 480s shoot closer to the sights being the exact bullet I use in my WR Match rifle and I was pleased to find the paper patches perfectly cut into ribbons just as they should be when we shot it.
The extra case capacity of the No.1 Express will allow me to really dial in a good load with plenty of oomph.

So, the stars aligned and this fantastic rifle was brought back to it's original state and purpose by a smith whom truly understands British rifles of the era (as well as the demands of his eccentric clients LOL!!)
What a wonderful rifle!

Before:

After: