Here's the sight on my Hepburn 45-70. Its from what I make out from Tom Rowes book a Match grade B, with shoulder rest, double set trigger, mid range tang sight and a Swiss buttplate. 

My question is, has anyone seen a sight like this, factory? It's like a ghost ring on a current shotgun ect. But definitely period correct, no markings I see though.

It fits perfect. It's neat and accurate, but the front sight I put on makes it too low to work with tang sight. So I'm likely going to take it off and store it when I get a long range tang sight.

Thanks Paul

might try querying Dick Binger about it.   

did it come with both the tang sight AND the barrel sight?

Thanks for the responses. I included three more pics. Yes it does have factory tang sight too. And with that said, the apertures are semetrical ( they line up as one, neat!!! ) 
I also included a top pic and a back view through it. 
Thanks again 
Paul

Its a bit odd looking since it is SO thick.  So thick, that with a closer look at the first picture, I wondered if it incorporated some sort of an an adjustable aperture. There appears to be a small slotted head screw at the 5 o'clock position in the rear face of the sight disc.
  I also suspect that it might be a post production sight modification because the hole looks to be slightly off center.

I have a break-open German  "stalking rifle" made originally in .22 Vierling (The German version of the 22 Hornet---commonly used in "running boar" competition since it was the lightest calibre allowed under German rules). 
It originally had a "blade & elevator-type" rear open sight. But that was replaced with "ghost-ring" aperture blade made from a silver-soldered in washer of some sort.  I can well imagine that it might have been great on moving targets with that type of sight. 
Unfortunately it was badly pitted an inch or so ahead of the chamber throat.  I have had Steve Durren reline it to 25-20 SS.  I also (after much trial and error) found a early German Claw-mount scope the could be adapted to fit the factory claw-mount bases.  

Does look like a Stevens H style tang sight. Wonder if the spacing is 1.5" Stevens too?
I don't see any signs of checkering on the buttstock or forearm, so don't believe it's a Match B Hepburn. The B had checkering on both buttstock and forearm. The A had just buttstock checkering. Wonder if someone added a small Farrow style Swiss buttplate to this gun to attempt to make it a Match rifle? Buttplate, stocks, etc. should be serial numbered to the gun on most Remington Match rifles. Mine are all serial numbered to the action and barrel.

Paul,
Indeed many Match rifles did not have forearm checkering, but those would be Match A, not Match B. The Match B have checkering on both buttstock and forearm, and a higher grade of wood.
What does your buttplate look like?
The factory spacing is 1.93" so it sounds like that "Stevens" style sight is spaced correctly for the Remington! Never seen one like that on a Remington!

Sight is kind of neat - question:  The elevator can be raised only so far and the notches on it are for minimum specific yardage.  How would one plan to use the sight to shoot, say to shoot steel to 500m and target to 1000yds?

Yes, the ghost ring style sight has the notches to click it up. Not too much obviously. However at the top notch it was real accurate at 50 yds in my backyard. The front sight I put on is a bit high for this so I removed both this ring and the tang sight. I replaced the original mid range tang with a Lee Shaver long range. Now I can adjust to ranges way beyond my 50 yard home range.  I was shooting 300 gas checked and 500 postell. The bores pretty nice for 120 years old, no pitting still shines a bit. The 500 shot in a two inch circle at 50 yds. Now the 300 I won't talk about...... So I'm looking forward to some longer range up coming. 

Oh yeah, regarding this sucker being a hunting rifle, I kind of doubt it. My son put it on the bathroom scale before we shot yesterday, just shy of 20 lbs. 
Its definitely fun to mess with these old dandys.
Thanks all,
Paul