I have here a rather nice old Dutch bed. Unfortunately, it seems to be
intended for a mattress of 115 cm width - the exact width available for
the mattress is 115.5 cm - I presume that such a thing used to be made.

Needless to say it seems to be impossible to find sprung mattresses in
that width (I have found a company that makes custom-sized foam
mattresses).

How exactly do mattresses need to fit? Would a 110 cm mattress be
visibly too narrow (I think it would)?

Thanks,

Daniele