Sight itself is obviously a 103, but an usual one; looks like one of those that attached to the cocking piece of a bolt action.  The one made to fit Krags & ’03s required the cocking piece to be sent to Lyman for fitting it, & that’s what you’ve got, I think.  (Though there was one also made for the Newton.)  Worth quite a bit, I believe, as they were not popular (slowed lock time), & thus rare now. 

25-35 said 
I have a Lyman disc tang sight on a Model 53 very similar to the one pictured above. I don’t currently have the rifle/sight to post a picture and am using and taking advantage of the posted picture above as a reference. Only difference, it has windage and elevation capabilities.  

No intelligent question requires an apology.

The one pictured above also has windage–that’s what “made” a 103.  But on a 53, it should be mounted on the upper tang…right?  All 103s with standard Win. upper tang hole spacing command a premium.

Chuck said

Thank you Clarence.  The sight is supposed to be for a Newton bolt action rifle.  The 1916 Newton is my only modern bolt action that I own.  The 256 Newton is a 6.5/06.   

Well, you’re in luck in one respect, because the one intended for Newtons required no machine work to fit.  That should make it easier to sell, but then again there aren’t vast numbers of Newton collectors, though I’ve always liked them.

25-35 said

Still wondering what it’s value add might be?  

Don’t wonder–search “Lyman 103” on ebay under the “sold” category.  Of course, auction prices vary dramatically, depending on who’s bidding, but “sold” listings are a place to start.

Chuck said

I knew of 3 Newton collectors. Bruce Jennings, Jim Foral and Larry Wales. 

Don’t know the others, but I know Jim quite well; think he may have written a Newton piece for Gun Digest.

Is there a Newton collectors website?  There is for about everything else that people collect.