If any doubt exists, a solution of copper sulfate (CuSO4), which can be purchased at any drugstore or chemical supply house, should be applied with a cotton swab to an area of the liner. If the liner is not plated, a copper color will appear. If it is chrome plated no change will take place. Never use chrome in chrome.
It is recommended that chrome plated rings not be installed in chrome plated liners under any circumstances. Catastrophic destruction will likely result. Plain cast iron-manganese phosphate coated, or molybdenum rings may be used. It is normally difficult to detect visually in a used cylinder if it is chrome plated or not.
Cylinders are normally chrome plated for two reasons. To increase service life or to re-furbish worn liners.