Knuckle Sandwhiched

Here's a very cool and interesting old photo

Pre-war? Bob Jobs, does it get any cooler?

I don't know the date of this photo but we can somewhat date the bikes.

The first hint is they all have rectangular foot boards, making them '39 or older. the Knuckle's paint (tank panel), doesn't look quite right (to me), for a '39 but, it does have '39 and up fender trim. The tank panel may be the police type patern. All the 45's have RL tanks ('36 and earlier) and I beam springers. Two have air horns. The farthest bike has the old top of tank mounted speedo and a custom air cleaner instead of the air horn. You can also see the pre- '41, flatter derby cover on the closest bike. It also looks like it has a '34 (single) or '33 and earlier taillight mounted up on the tip of the rear fender. All three 45's have cool old style flamed paint jobs.

Did I miss something? Maybe the good doctor has something to say.