Purchased in a private sale in Witney, West Oxfordshire, along with a load of other interesting looking vintage tools and scientific equipment.

The condition is as you can see in the photos. I can't confirm if any parts or missing, but please do your own research online. Thanks.

I have Googled a photo of this and the results were as follows:

This is a Horstmann adjustable thread caliper gauge, designed for checking screw thread tolerances.

The device consists of a cast steel body with hardened steel measuring anvils, often housed in a wooden storage box. This one luckily comes with the desirable wooden box.

It operates by measuring if a thread passes ("Go") or does not pass ("No Go") through the set anvils to ensure it meets specific industrial standards. Similar vintage tools are often sold used for industrial metrology purposes.

Green Wax/Seal: The green material visible at the top is a tamper-evident inspection wax. It is melted over the adjustment screws after calibration to ensure the settings are not altered or tampered with during use on the workshop floor.

Manufacturer: Made by Horstmann, a historic British engineering firm well known for manufacturing precision gauges and clockwork mechanisms.