24-Scale All-Plastic Engineer's Rule (Darmstadt)
Teledyne-Post model 44CB-200 [1972+]  (some [1972] marked 1420)
Hemmi model P261

 I'm not aware of specimens with the 44CB-200 model number; the inital lot (marked "1420") may have lasted until the end of slide rule sales about 1975.  However, Post may well have sold "1420" rules in boxes marked "44CB-200.   

The scale set is "Darmstadt" (a word Post never used)--similar to the Versalog.
1972 Teledyne-Post Slide Rule Catalog 

Teledyne-Post 1420.   Date code "^UI" (September 1970)