Dynamic blocks may not survive a round-trip to AutoCAD 2005 or earlier if the block definitions are modified in the legacy environment. This caveat applies to modifications both by users in the legacy environment and by applications that treat dynamic blocks as if they were legacy blocks.
To help smooth the transition to earlier AutoCAD versions, the AcDbDynBlockReference class provides functions for preparing blocks for use in legacy environments. These functions let the application change existing representations to reference the original block record, change the reference for a single block instance, and refresh a single representation to point to the original block. You can also disconnect a representation from the original block definition and convert it to a nondynamic, or static, block. When you disconnect a representation, AutoCAD creates a new legacy block definition and replaces the representation with a reference to this new block. You have the option of either providing a name for the new block or letting AutoCAD maintain it as an anonymous block.