They look like boxes for storing library books to me! The number doesn't register as a current VOCAB number.

Being made of ply wood and those infamous initials of MFI makes me think that they're modern and not necessarily MoD either

For you wild and unwashed colonials and heathen antipodeans out there in Forumland, MFI is a UKicon manufacturer of cheap utility furniture. It's usually flat-pack with loads of the correct fixtures and fittings missing too. Hence the initials, said to indicate 'minimal fuxxxng interest'