[Jim McDougall]

As an arms historian, my greatest pleasure is seeing examples which are often in rugged to excavated condition, as these are the ones which give us the look into real time history. These two are classic cases, and after the research I have done on them, I am inclined to agree with Marius on the 16th century period.
The 'ballock' dagger (a term altered to 'kidney' dagger by uncomfortable Victorians) apparently has been around since about 1300. It seems that by around latter 14th they were well known on the Continent and in the British Isles.
In looking into the marks on the blade of the one example, these marks are placed in accord with what seems a standard marking location on knife blades of these times. According to "Knives and Scabbards" (Cowgill; DeNeergaard and Griffiths, London, 1987, p.20)...marks became increasingly common on 14th c knives and by end of century over half knives were marked". It is also noted makers of Cutlers Company were compulsory by the end of the 16th century.

It is interesting that this pair of marks (which I could not find in this reference nor others at this point) seem to be a bell, and rather than a 'T', perhaps a 'tau' cross. These kinds of marks and others with ecclesiastic connotations may be associated with the fact that churches were often responsible for weaponry and materials and blacksmiths and arms furbishers were part of these compounds. While these seem more in league with guild or cutlers type punzones, it is possible they may be in this category which was of course not recorded in such manner, and simply property type marks.
I am not sure how these might be compared, but it seemed worthy of note.

H.L.Peterson ("Daggers and Fighting Knives of the Western World", 1968, p.28, notes that in early years of the 15th century grips were flared into an inverted cone shape ending in a flat butt usually covered by a metal plate.
(as these seem to correspond to). In the early 16th it seems that the basal part of the hilt began to have extended 'arms' parallel to the blade, so these may be latter 15th, though transitions were varied according to regions etc.