def case(bin_spec, default='nf'):
    """ Return the case specified in the bin_spec string """
    c = default
    if 'NF' in bin_spec:
        c = 'nf'
    elif 'ÞF' in bin_spec:
        c = 'þf'
    elif 'ÞGF' in bin_spec:
        c = 'þgf'
    elif 'EF' in bin_spec:
        c = 'ef'
    return c
