Pocket Versalog Duplex
Frederick Post model 1461 [1957-71]
Teledyne Post model 44DA-610 [1972+]
Hughes-Owen model 341-3050
The Pocket Versalog was made for Post by Hemmi.  There is no exact Hemmi equivalent but Hemmi model 149 is very similar.  They were both created about 1957; before then Hemmi didn't make any pocket duplex rules.

The Pocket Versalog first appeared in the 1960 Post catalog but was available starting about about 1957.  Variations correspond exactly to variations in the full size Versalog (model 1460): Variation  "IA" with navy COS scales from 1957 to 1960; "IB" with green COS scales from 1960 to 1968; model II with an "A" scale from 1968 until the end of business.

Exposed Bamboo Edges:  Several Hemmi and Post pocket duplex slide rules used the same blanks as the Pocket Versalog.  When first intruduced, the bamboo core was exposed on the edges of these rules but later models had all four surfaces covered with celluloid veneer.  Exactly when the edges became covered is unknown but my friend, John Spivey, has a "bamboo-edged" Post 1461 with date code "LL" and a celluloid-edged Hughes-Owen 1778 date coded "NC"--placing the switchover date between December 1961 and March 1963.
1960 Frederick Post General Catalog,  Pages 80-81
Pocket Versalog "IA"   Edges are bare bamboo.
Date code "IG"  (July 1958)
Pocket Versalog "IB"  Note green COS scale. 
Date code "RE"  (May 1967)
Pocket Versalog II.  Note "A" scale.
Date code "VK"  (November 1971)