Digital pH Meter - Water Quality Management

This is a pH meter. It was found during a home organization, but I don't know how to use it.
It seems to be usable in various fields such as swimming pools, aquariums, hot springs, rivers, hydroponics, aquaculture, goldfish bowls, etc.
I'm selling it cheaply because I don't understand it well.
[Anonymous Shipping]
[Instruction Manual Included (English)]
[Battery Replaced]
Selling due to home organization and decluttering.

It shows signs of use. The battery has been replaced. It has been tested for power by submerging it in water. (See images)

? This is a used item stored at home. There may be minor scratches and dirt that are not visible in the photos. If you are concerned, please check the condition and appearance of the item in the photos provided, and refrain from purchasing if you are concerned.
? As this is amateur storage, please refrain from purchasing if you are sensitive or seeking perfection.

It will be shipped in simple packaging after waterproof packaging.
Shipping is anonymous.

Please consider it.