Copper Document/Map/Lab Tube

Bought this copper tube yesterday. It's 41.5 cm (approx. 16.33")
Some similar tubes are on Ebay with the description that it's military/nautical use, but I also found these 2 https://www.estatesales.net/marketplace/items/419906 & https://www.estatesales.net/marketplace/items/419903, with the info that those tubes were used in labs
The mark on both ends could probably tell more about the exact use, but I haven't been able to find any similar marks on the www.
Does anyone recognise the mark (B between two triangles? and the number 54)

 

it's cool and all...... but still looks like a pipe b0mb

 

Multifunctional!
Document tube and pipe bomb

 

Still no luck finding that mark ...

As some of these tubes seem to have a military link, is this B-mark something you recognise in that field, @daveydempsey?

 

Thanks. Would be great if it were a variant to the known broad arrows or a somewhat blurred version, but as these appear to be solid triangles, cjhances are slim there will be a connection, right?

Only now I noticed that there was some type of fiber material in the tube. It looked like a small piece, but it kept coming out ...bit by bit, as it desintegrated. The final part came out like this


Unfortunately it wasn't hiding anything ...

 

The bottom has a metallic/mirrory shine. No idea why, as the whole thing seems to be made of copper