Dear Ron and Pier,
Thanks a lot for your inputs and comments on this teppo.
The mei is bitten by rust, it makes craters, so some kanji disappeared and it is very difficult to read and more difficult to take good photos.
The split Bisen breech screw is stuck by the rust. I don't know if I could remove it. I won't break it.
Thanks also for the numbers translation. Is it frequent that teppo got a such registration number ?
I confirm you the ramrod is present, but due to patina of the wood, I guess it is not the original one.
It appeared that the stock is in 2 parts: one for the barrel and one for the mechanism.
I think you are right; it must not be the original one and, as you said, could be an older barrel restocked and / or repaired at some point in time.
Many thanks for the illustration from Sugawa San's Book. The hole on the right is only drilled halfway through, about 2 cm deep, and fully covered copper in the side and the bottom. I noticed the light ring on the stock and you are right again, the decorative ring is missing from around this opening.
I am at office at present, but when I come back to home I will measure the caliber and check if it is charged or not, and let you know.
Thanks again
Sébastien