# ``bottle_number``
## Properties
:dimensions: N_PROF, N_LEVELS
:dtype: str32
## Default Attributes
| Attribute | Value |
|-----|-----|
|``whp_name`` | ``BTLNBR`` |
## Description
The bottle identification number. This is intended to be a permanent, unique serial number fixed to the sampling device. It may also be the an identifier fixed for the duration of a single expedition. Allowed characters are U+0030 to U+0039, U+0041 to U+005A, U+0061 to U+007A, and U+005F (``0-9``, ``a-z``, ``A-Z``, and ``_``)
:::{warning}
Despite the name, the value IS NOT numeric, ensure that any software reading the file can handle UTF-8 data of the specified allowed code points. The CF/netCDF files force the data type to be char, but for historic reasons, the variable name is maintained as bottle_number.
:::