I'm not sure which Lyman sight you have.  This may need to be removed or elevated to remove bolt.
Bolt Removal: Open bolt and draw it to the rear. Hold Krag with trigger guard against your belly and magazine door up. Your right fingers should grip the action and your extended right thumb rest on the bolt face. Your left little finger and ring finger should hook over the stock comb with the bolt handle pinched between your left thumb and index finger. Pivot your right thumb away from your body so it engages and lifts the extractor (the hook and long flat spring that rotates on the bolt). At the same time rotate the bolt by pushing the handle away from you with your left thumb. The single locking lug will ride up the incline of the receiver wall and the extractor will swing on its pin, allowing the bolt to be withdrawn rearward from the receiver. Re-install by inserting bolt into the action with the locking lug in the 12 o'clock position. As the lug clears the receiver bridge, rotate the bolt. The lug will ride down the incline and the extractor will rotate and snap into position.
Instructions: Go on eBay and enter 'Krag'. Lots of manuals and instructions are listed. The old NRA disassembly manuals have good instructions for the Krag. You can probably Google search, find, and print. Welcome to the Forum.

Thanks for getting back to me. I failed to mention that my Kraig has been "restocked" with a true hunting style stock. I will try to post up pictures this weekend. From your description of the bolt removal I now know the sight must be removed. This rifle killed many a deer in my grandfathers hands in PA and MD in the 40's and early 50's.

I'm guessing your Lyman sight required drilling and mounting on the left side of the receiver, since you mentioned it covers up the serial number.  Holes drilled and tapped into the receiver damage the collector desirability of a Krag.  On the other hand, your Krag is a family heirloom, since your grandfather and father hunted with it, and hopefully you will continue the tradition.  If your Lyman sight is a Model #33 or #34, it has collector value ($100 - $200) depending on condition.  Of course 'Sporterized' Krags range from butt ugly crude to fine workmanship classics.  It would be interesting to see pictures of your Krag.