K&E 68 1648 (4153-1) 5" Plastic Polyphase Mannheim 1962
This rule came in a box marked 68 1648 yet the rule and instructions are marked 4153-1. During the early years of the new 68 series numbering system old stock was shipped under the new numbers.
These scans are from the collection of Clark McCoy
Back side of slide
End view of case
Cover page of manual