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: Overall length 48", Scale length 42-3/8"
Model 1447DA: Overall length 72", Scale length 63-1/2"