All About Slide Rules Book (PDF)

[Benjer]

68 1555 would be the model number. The old model number is 4168.

043482 is the serial number. K&E generally started serial numbers at 0, went up to 999999, then started over. They rolled over several times through the decades.

Presuming your slide rule was not made before 1962 (when K&E switched to 68x model numbers) I would guess it was made after 1965 based solely on the serial number but this gives no indication of its sales date. From what I've read serial numbers aren't a strong method of dating K&E slide rules in any event.

This link contains much more information than I can provide.