Naka-ya Meito 8-inch Double-edged Saw from a Renowned Sawsmith Family

This is an 8-sun double-edged saw from the blacksmith Nakaya Shintaro Mei.
At first glance, it looks like a very ordinary tool, but it's an interesting tool with strange and inexplicable points.
The blacksmith was active around the mid-Showa period.
It has considerable age, but there are no signs of use, and except for the handle, the blade is almost new?
Yet, there is a deposit slip attached from when it was sent for sharpening. The sharpening fee was 2000 yen, which would be about 5000 yen at today's prices. Did someone pay such a high sharpening fee?
When I tried using it, the sharpness was quite poor.
It wouldn't cut.
So, when I started sharpening it, I was surprised.
The bevel on the cutting edge was ground in the same direction on both sides.
It wouldn't cut like that! When I re-ground it, it was revived with a sharpness befitting the brand. A valuable tool with an interesting story.
Overall length: 615 mm
Blade length: 240 mm (8 sun), double-edged
Blade width: 88 mm
Teeth per 30 mm: 21
Chisel mark: Nakaya Shintaro