This is a scalar DisplayString value sitting at the top of the discovery branch, described in the source only as a generic 'Character string value' with no further detail. In this Sun/SunSOFT discovery MIB the name suggests it acts as a signature or format marker so an NMS polling agent knows what version of the discovery data schema it is reading before parsing the discoveryTable rows. As an illustrative example, a management station might use its value to decide whether it can safely interpret the entries in discoveryTable or needs a compatible parser for an older format.