It would be interesting to see credible documentation that Ross rifles were converted for cadet use. I do not hold myself out to be a Ross rifle expert, but I have never seen or heard of any such documentation or converted Ross. Any cadet conversions of Sniders or Lee Metfords I have owned or seen were crudely done in comparison to the subject rifle and, as I recall, significantly shorter. Furthermore, the military would have no reason to remove the butt markings during such a conversion, and every reason not to. There is also an obvious question to be asked. Why would the Ross Rifle Company upgrade a Mk II to Mk II* for cadet use?
Some points of clarification:
We can leave the Mk II** out of the discussion since it is a purpose-built target rifle and differs from all the rest.
The Mk II**** (4*) did not have peep sights. It had the Mk III Ross rear sight, which was rejected by the military. The rear sights were subsequently replaced with the H-type Sutherland sight and the rifles were re-designated as Mk II *** (3*)
The rear sights on the Mk II*** (3*) and the Mk II***** (5*) were U notches when in the down position. The aperture, if so equipped, was only available when the staff was raised to the upright position. Although I may be incorrect, I believe the 3* was equipped with the Sutherland Mk II sight, which has an aperture, and the 5* was equipped with a Sutherland Mk I sight, which did not have an aperture.
If I am not mistaken, the Mk II (no star) and the Mk II* were the only Mk IIs to be equipped with the Ross MK II rear sight. The Mk II rear sight had durability issues.
The only Mk II to be equipped with the Ross Mk III rear sight was the Mk II**** (4*), as mentioned above, and that model was most definitely not re-designated as a Mk II*. The Mk II and Mk II* are easily distinguishable from subsequent marks (2* through to 5*). Amongst other things, they have a much narrower mid band and an abbreviated upper band.
Mark II rifles were available for private purchase, and presentation rifles do show up. Such rifles tend not to have the military-style butt markings and are sometimes found with attached presentation plaques. The lack of butt markings on the subject rifle and the four holes on the right side of the butt might indicate the subject rifle was a private-purchase presentation rifle. If that is the case, one would expect to find a serial number on the left side of the barrel just ahead of the receiver and just above the stock line. It would also explain the apparent serial number under the butt plate and might explain the lack of a rear sling swivel. Some, if not all, commercial rifles had the serial number stamped on the butt under the butt plate - in addition to on the barrel. If the rifle were mine, I would carefully remove the rear hand guard and look for a serial number. The rear hand guard wood is thin and allowing the spring clips to snap shut can cause the wood to split longitudinally. remove the hand guard slowly so as to allow the spring clips to slowly relax.
Whatever the case, I continue to believe the barrel and stock were shortened after the rifle left the factory, and, if military, not while in military service. The evidence currently points to private purchase.