These were large slide rules carrying the same scales as Frederick Post model 1447 Student Slide Rule
They were made of painted softwood--probably in the United States.
They don't appear in any catalog or dated material: I guess they were available from about 1950 to 1960.
 

Here are pictures of specimens the Slide Rule Trading Co sold many years ago.  I apologize for the quality.

Model 1447D

Model 1447D:  Overall length 48",  Scale length 42-3/8"
 

Model 1447DA

Model 1447DA:  Overall length 72", Scale length 63-1/2"