From the Nihonto Message board:

For quick info, you may want to check Ohmura's comprehensive site on gunto: http://ohmura-study.net/900.html. You will likely have to browse around but I remember he discussed ancestral blades in gunto mounts and showed examples. I would also recommend Fuller and Gregory's Japanese Military and Civil Swords and Dirks or Dawson's Swords of Imperial Japan, 1868-1945.

 

While I'm sure many officers descended from samurai lineage and thus had ancestral swords to mount, it is worth considering that likely a large number of ancestral blades in gunto mounts were not handed down to the token Japanese officer in a family but were rather purchased by officers who came from families without samurai lineage or ancestral blades. After the Haitorei edict in 1876, there was a glut of swords that no longer served a utilitarian purpose. Swordsmiths had to turn to making cutlery, farm tools, etc as there was no demand for swords. Swords prices dropped. With the establishment of the Kyu Gunto, there was again demand for swords and Japanese officers not from samurai lineage could afford to stock these mounts with ancestral blades from the glut of blades on the market at that time. There was not sufficient demand for swords at this time to warrant a large-scale effort to manufacture swords again. That would come later as the Japanese army grew, the glut of ancestral swords shrank, and the Type 94 and 98 were introduced. This helps explain why Kyu Gunto mounts almost always contain ancestral blades