Hi Raimey,
Who knows how many of those are still around?
Considering the 20th Century turmoils, I would not be surprised if less than 10% of the fare was still around. Probably much less, actually...

I don't recall having ever seen an LB stamp on a single barrel...
It does not mean that the shop did not sell those as individual tubes to the trade, but I sincerely doubt it as high ends makers tend to like to capture all the value they can.
Best regards,
WC-