The glycerin-filled pressure gauge is a precision instrument and must be stored frost-free.
ABS casings will absorb moisture so the casing must be punctured to prevent damage.

A simple way of checking the gauge is to mount a completely new set of nozzles, which are known to match the values of the nozzle table.
At a fixed working pressure – e.g. 3 bar – the nozzle flow rate is calibrated with a measuring jug.
If the flow rate of the nozzles matches the table value at this pressure, the pressure gauge is OK.