I just wanted to join in, and as Jens has noted, most that can be said on this sturdy tulwar already has been said. I agree it is of 19th century, probably late, and the blade is of cross section and profile that seem pretty well established on tulwars of this period. By this time, the British Raj had created considerable commercial enterprise with weaponry and outfitting for the occupying forces there.
I wonder also about the square nut on the pommel. It seems tulwars typically had a capstan with pierced hole that I understand was for unscrewing and disassembling the hilt. Is it possible that this square capstan might have been for similar purpose but with more industrial application, a socket or wrench?
If indeed weapons were kept disassembled as has been discussed (I would presume this practice was applied in some cases but certainly not universally in various armouries) then such a feature would better facilitate assembly.
I honestly have not seen the square on tulwars either, but knowing the volume of munitions activity undertaken in arming the many Native Cavalry regiments for many years it was undoubtedly quite an undertaking. There were specific regulations for tulwars to be carried by these cavalry and I have seen listings indicating which type swords were to be carried. Some units had selected the standard tulwar, and blade lengths varied..I believe that Bengal for example were 31" while Madras was 33" or vice versa, cannot recall exactly. While the question concerning military inspection or armoury marks would be valid, many times such markings did not appear on weapons.
If interchanging blades to meet regulation when arms moved to other armoury, perhaps an explanation?
Just thoughts!
In any case, a solid example!
All best regards,
Jim