Do either of the barrels have Niedner stamps under the forends? ... looking for a barrel number.

... Joe D

In my opinion, The "55" is a custom rifle.  The "engraving" on the "model 55" appears to be etched rather than engraved which would make it very rare if original. It is true that some models listed as engraved could be had plain (I've seen a Model 52 without engraving) as well as plain models factory engraved  on special order.  Same with wood--I have a Model 47 with factory fancy checkered wood instead of the cataloged plain wood.  However, from the rather poor photos in the ads, I am must say that the stocks simply do not look quite like any factory stock that I'm familiar with. 

The crown on the muzzle of the "55" is not factory work.   

Finally, the Model 45 had a straight bottom tang.  This means that if the face of the receiver is marked "45" the bottom tang has been replaced or modified._

Unless there were some solid proof that they came from Niedner's shop or the shop of another well known smith, they are worth whatever they will bring a curios or shooters.  From the appearance of the stock on the "55", I'll bet that the matching numbers on the wood were applied by whomever made the stock and not at the Stevens works.

On the other hand, the "Favorite" may  be original-hard to tell without having it in hand.It appears to be a No 418 "Walnut Hill" Junior Target Rifle.  These were made in the 1930's on what was basically the 1915 coil spring Favorite action.  These were the "baby" versions of the celebrated Walnut Hill Models 417 and 417 1/2 rifles.   
   
Be careful, 
Leon (ACGould)

I have a .22 Ballard that is stamped on the top of the barrel, "Neidner Rifle Corp  Dowagiac, Mich." under the forearm there is a number stamped.