That's what I thought too...
I also thought an SM420 was NOT synchronized in 1st to second or 2nd to first, both of the ones I have and have driven I had to double clutch to make those shifts, and I never worried about if it even had a synchro or not, as I assumed it did not.

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-