Your carbine number is not listed in Mallory's book, but that's not
surprising since most Krag numbers are not.  There might be some other people here who have access to more complete SRS (Springfield Research Service) numbers and i am sure you will hear from them.   The 1901 rear sight is commonly found on many Krag carbines of the same vintage if reworked after 1899, but I do not use Poyer's book so I can't help with answers to the questions you have.  Usually, the common, Carbine hand guard for the 1901 Carbine sight is referred to as the "humped hand guard" for obvious reasons.  There are almost as many hand guard varieties as there are models of sights. The 1901 Rifle sight does not use a humped model guard.