I just received a side handle 4x5 Speed Graphic from ebay.
Its serial number is 56090 This serial number comes up in the middle of an order for 200 fingerprint cameras in 1916.
The lens is a Wallace Heaton No1 Zodellar - Anastigmat 135mm f4.5. Its in a Dial set Compur with a top speed of 1/200. The serial number of the Compur is 628374. There is no serial number on the lens.
The lens/shutter is mounted on an aluminum lens board stamped HR enclosed in a circle on the top right corner and a HR solenoid is on the bottom of the board.

According to Graphic Model history https://graflex.org/speed-graphic/graphic-models.html the side handle started in 1928 and is confirmed by catalogs at http://piercevaubel.com/cam/catalogs.htm
According to Compur serial numbers available on line the shutter is from (edit) 1925.

Charles, are you sure that the s/n isn't mutilated? 156090 is a 1926 s/n, but for a 3x4 RB Ser. B.

As for the shutter, P-H Pont's chronology says 1925. Since it was almost certainly a replacement for the camera's original lens, its date seems irrelevant.

Photos and link removed.

Paint on the serial number removed with Acetone Nail Polish remover and a cotton swab.

There is a 3/8 rounded brass on the bed under the focus shaft near the edge of the bed. My 1936 Speed (4x5) does not have this on the bed.
EDIT: Turns out to be a brass head thumb tack. Someone replaced the retainer pin for the focus knob with it. I will make and install a new pin.

Its definitely an early side handle Speed Graphic.

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56090 is also stamped on the inside of the back.
Flickr album now public.