- s/n 119712 (1d S): no hole,
- s/n 127195 (ordinary 1d): hole.
So, it seems the change appears somewhere in the 12xxxx range.
There is no connection with the material of the shutter box (brass or aluminium): the 119xxx has an alu shutterbox, but no hole. And there is no relation either about S or non S: the shutter box are exactly the same, but not the speeds, of course.
Of course, it would be interesting to check with other Fed 1d...
If all that is verified, it could mean that there is no B possible before that range. So, Alain could be right when saying that JLP's B was not genuine...
Thanks to have put the question, Ulrich!
Amitiés. Jacques.