Export mesh Instances. The first Instance of an object exported has a mesh, but all other Instances do not.
In Blitz3d, the other Instances copy the first Instance's mesh using CopyEntity - thus they all share a single mesh.
Instances retain their position, rotation, and scaling; they can also be animated.
Prefix: B3D_INSTANCE_[num]_
[num] is the Instance number - all objects that share the same Instance number are Instances of the same mesh.
The first Instance of an object exported has a mesh and is given the next available prefix (e.g. B3D_INSTANCE_1_).
All other Instances of that object are exported without a mesh, but share the same prefix.