Now with "No. 5" stamped on the spindle housing.  Some of both the No.1 and No.2 types were similarly impressed. There are no other markings.  The tapered crank is not marked, either.

The chuck is the no-springs, three-jaw variety, with diamond knurling.   The frame is the strengthened version, similar to the No.1's frame.

Found and photographed by T. Ralph Stumpe; thanks to Ralph for permission to publish here.