I am starting a project and I want an express sight. I found a Mauser sight at numrich I like. However, it came minus a base. Normally I would just wait until someone got the base in stock but my curiosity is killing me. What does the base even look like? I'm either not googling the correct item or I'm just stupid. Can someone point me in the right direction? Thank you in advance.

I suspect you’re talking about the front sight. Midwayusa and Brownells should have what you’re looking for.
As far as the rear sight there’s a couple options all but one of my lever action center-fires have steel aperture sights -maybe one aluminum, I don’t remember.
If you buy a aperture sight that mounts on the receiver all you’ll need is a couple of threaded holes.

Look seriously at NECG - they have excellent sights.

Good advice.

https://www.newenglandcustomgun.com/categories.php?cat=5

Sorry I wasn't very clear....and our internet went down the last couple of days. It is the rear sight. 100 yard fixed and the 200 and 300 both flip up. For the life of me I cannot find what a base for it is supposed to look like. At this point I think it's time to just mil some thing out myself. It's not like this is going to be a period correct build or anything. Thanks much for the heads up on NECG.

I had two sets of sights like that. I did not like them. I replaced one with an aperture sight - the Winchester.

The base of one of my flip up sight (old Winchester, I believe) fit into the standard cut in the barrel. The other was on a Ruger African 77. The solution on the Ruger was to epoxy the 200 and 300 sights from coming up.
It seemed to me that if a shooter was in a hurry the sight might be in the wrong position and the shooter may not notice it. Just my two cents.

Jim Wisner's pre-64 M70 African rear sight is an extremely nice piece.

http://www.wisnersinc.com/model/custom-rifle-parts/

One on my M70 416 Remington.

That has got to be a rush dealing with buffalo. Thanks for the replies. As soon as the barrel arrived I will try my hand at milling something.

Look at what Recknagel have - they make a ton of sights, amongst other things. NECG rebadge and sell some of their products but not all. We have a Recknagel retailer here in Australia, so would expect at least the same in the US.

NECG is the retailer here.

The sights you described are likely the ones put on the Whitworth interarms express rifles. The base is essentially a big dovetail for what you have in your hand.

This is what the Whitworth sight looks like in its base:

It is easy enough to make a dovetailed base for the sight insert.

Oh yeah! That looks like just the ticket. Thanks a million!

https://postimg.cc/gnrT5khQ

NECG has exactly hat you’re looking for. Worth a phone call if you’re not completely sure after you look at their website. Good people to deal with.