How is the hydrostatic test date identified on a scuba cylinder?

The hydrostatic test date is most commonly identified by a stamp on the cylinder neck. This stamping method provides a permanent and tamper-resistant means of showing when the most recent hydrostatic test was conducted. The stamp typically includes not only the test date but also the test facility's identifier, ensuring that any future inspections or inquiries can be traced back to the relevant testing authority.

While a decal, green and yellow bands, or etching on the cylinder base might be used for other types of information or labeling, they are not standard methods for marking the hydrostatic test date. The neck of the cylinder is specifically chosen for visibility and accessibility, allowing divers and inspectors to quickly verify the testing status of the cylinder before use. This practice enhances safety by ensuring that diver equipment is up to regulatory standards.