Well first and foremost, the Bernard Coin Box has been around (to my knowledge) since the early 1960's. However, Bobby didn't get these produced in great numbers and sold them only to friends at the Magic Circle or to his students. At one time, Pat Page was actually having them manufactured for him and Ken Brooke sold a few - albeit they didn't appear in Ken's catalogue (a few items Ken stocked never did actually).
Bobby's idea was for an improvement to the standard Okito Box that:
(i) entailed only one lid reversal move
(ii) enabled coins to be loaded easily inside the box
(iii) enabled coin changes without the use of gaffs
(iv) could double up as a Boston (or German) box if required yet be shown in the same manner as you would a standard Okito base
The basic modus-operandi was that the base of the box wasn't actually a solid - it moved. It's construction was such that the box was basically a piece of brass tubing (slightly lipped) with a disc inside that fell easily from one end to the other when reversed.
To this end, imagine filling the box with coins then performing the reversal as the lid is placed on. The coins could (as with any Okito Box) be stolen; thus enabling the inner disk to fall to the bottom. If the lid was immediately removed, you'd see an empty box.
However, I also saw Bobby use one as a Boston Box - clearly, as the base moves, one coin can be placed within the automatic 'temporary' recess.
It has been renamed a 'BO Box' - abbreviation for Beyond Okito.....but Bobby never called it by this name. I had a rip-off version a few years back but sold it a year ago. The quality was absolutely dire - the outer tubing was so thin that the disk actually fell out a few times! Maybe that's why they are now sold with a genuine box to switch in. As far as I remember (and I'm going back around 34 years now to 1978) the one that Bobby used was finely machined and, whilst obviously not open to inspection, it appeared a solid box. It was also weighted superbly - unlike the junk now sold by the pirates. I cannot remember Bobby ever switching in a standard duplicate box.
Hope that this limited info is of some help. Let me know if anything needs further clarification.