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-100.
|1972 Teledyne-Post Slide Rule Catalog
Top: Teledyne-Post 1410. Date code "^UI" (September 1970)
Bottom: Teledyne-Post 44BB-100. Date code "^XE" (May 1973)