Symantec Endpoint Protection Versions

Symantec has a full list of Symantec Product Versions and release dates at Symantec Endpoint Protection, however, the Symantec Endpoint Protection Wikipedia page appears to be maintained more frequently.

RTM – Release To Manufacturing

MR – Maintenance Release (replaced by RU)

RU – Release Update

MP – Maintenance Patch

PP – Point Patch

Source: Symantec Endpoint Protection