def case(bin_spec: str, default: str = "nf") -> str:
    """ 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