Hemmi model P280
This appears to be another example of changing the model number after the slide rule had been manufactured. Specimens with both model numbers exist but I'm sure Teledyne-Post never sold this rule under any model number other than 44BB-140.
|1972 Teledyne-Post Slide Rule Catalog
Top: Teledyne-Post 1414. Date code "^VD" (April 1971)
Bottom: Teledyne-Post 44BB-140. Date code "^XF" (June 1973)