Hi Henry,
what does the Mimi look like? Does it show any linear Tekkotsu (Senkotsu) or evidence of folding?
This would not be an indicator for any specific generation, but would be a nice feature to study.
As for the generation - I think this is hard to judge because there are so many exceptions from the rules...
The shape of the Seppa-Dai created by the first generation tends to be elongated, narrow and gets pointed towards the "Ha"-side. This is due to the geometry of earlier Saya that broaden towards the Mune of the blade.
The connection points of the Sukashi usually get wider when they meet the Mimi.
From the second generation onwards the Seppa-Dai tends to get wider in shape.
The thickness of 0.5 cm fits to the early masters but the majority of the early pieces is quite thick (> 0.6 cm). I have also seen a Ko-Akasaka which was 0.4 cm in thickness but then had a diameter of more than 9 cm.
As for the Kebori, we can observe many, fine and well preserved carvings. Pieces of the first generations of the Akasaka school usually show a rather faint Kebori.
My guess would therefore be second/third or later generation Akasaka.
Hope, my thoughts help a little...
Cheers,