Looked at the pictures, not so sure it's a Spicer auxiliary after all. Is is covered in grease, so a tag should be hiding somewhere.

It's a single speed rear axle.

Lever on column is probably some sort of trailer brake actuation valve, possibly for vacuum trailer brakes?

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-