Not that you won't get help here, but this site deals a lot with O3's and Krag conversions.
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I would suggest posing the question on the Double Gun forum as well as there
several very knowledgable collectors with expertise in your rifles area. 

JLouis

I must disagree with Lefty38-55.  This is a very uncommon piece of quasi-US militaria, designed by H. M. Pope, made & marketed by J. Stevens in the 1901-1904 time period.  A Krag so converted, especially if a National Guard conversion (don't know how to tell), is a lot more desirable to a lot of real Krag fanciers than just one more original rifle.

These barrels have a definite link to historical single shots.
If it was not for these barrels, there would never have been any Winder Muskets and probably no Stevens 414s.  Without the impact these barrels had on smallbore rifle shooting, we might never have seen the 1922 series of Springfields or the Winchester 52.

The principal purchasers and converters of these rifles were National Guard units in Ohio, Michigan, Washington State, and (IIRC) Pennsylvania or maybe New Jersey.  The conversions were authorized by National Guard commands at the state level, but the Army Chief of Ordnance decreed that the converted Krags belonged to the US Army and ordered them restored to service standard.

But the Guardsmen trained with the converted Krags shot very much better than any units, Guard or Regular, that had not used the converted Krags.  Not even the Army brass could ignore success.  The Model 1898 Gallery Practice Rifle was produced 1908-1909 for the National Guard, but was too little & too late.  Winchester produced the Winder Musket from late 1904 on, with the first modifications made in response to a request from the Ohio National Guard.  Stevens went after the same market with the 414.

A surviving converted Krag is a real piece of smallbore history.

You need to see a close up of the breech with the bolt open.  The photo should show the location of the .22 chamber, being offset to the top.  Another photo should show the muzzle.  Photos of other parts would look like an ordinary Krag, either as-issued or converted.

All the rest is (if a military conversion), made up of standard Springfield Arsenal parts. The action can be any US Krag action.  The bolt is an ordinary Krag bolt, and used an ordinary Krag center fire firing pin.  The regular Krag extractor is used.  The chamber is offset to let the regular extractor grab the .22 rim.  The lower part of the offset chamber lets the regular firing pin hit the bottom part of the .22 rim.

All the external dimensions of the barrels are the same as the standard Model 1898 rifle (30") and carbine (22") barrel.

IIRC, there is a 3/8" dovetail for the front sight.  The barrel should be drilled & tapped for the standard Krag rear (barrel) sight.  There should be a "Stevens-Pope" stamp on the barrel and a serial number on the bottom side.

The Model 1898 Gallery Practice Rifle has an entirely different appearing breech, with an extractor that looks a lot like that on a .22 rimfire Winchester Single Shot.  The GPR action is marked .22 caliber on the left side.  The issue stock will have a "22" stamp.  Other parts may also be stamped 22.  Except for the actions & barrels, the GPRs were put together from left-over or reject parts

GPRs are also found with custom stocks.