Which version do there exist of the 991R2 receptacle?

The 991R2 receptacle is available in 4 different versions.
All versions have the same dimensional and mechanical properties,
but the mounting method of these receptacles is changes.

991R2 - dimensions

1) Plain holes for mounting with rivet or screw:

991R2-1AGV, 991R2-3AGV, 991R2-1BP & 991R2-3BP

991R2 - plain holes

 2) Chamfered holes for mounting with countersunk rivets or screws: 991R2-4AGV

991R2 - chamfered holes

3) Weld nibs: 991R2-2AR & 991R2-2AZ

991R2 - weld nibs

4) Plain surface for welding: 991R2-5AR

991R2 - flat surface for welding