18 Automatic / D-180:18" x 8.5" x 8" Front Wheels?

["D"- Man 827]

I have a couple pairs of wheels for the 18" x 8.5" x 8" tires, one pair has a flat area on the outside and one pair has a recessed area around the wheel.  I noticed the same on my D-180 front wheels.  Is it possible the rims with the flat area were originally on an 18 Automatic and later models used the rims with a recessed area?  See pics.  Hope it is evident what I am referring to.
 

[gwest_ca-(File Mod) 11,475]

Wonder if these 2 pages are involved
http://www.wheelhorseforum.com/files/file/1668-wh61-90-147-model-1-0610-18hp-front-wheel-failurepdf/

Front axle
http://www.wheelhorseforum.com/files/file/954-wh61-90-162-18hp-auto-d-series-axle-spindle-modspdf/
and
http://www.wheelhorseforum.com/files/file/1651-wh61-90-232-18hp-auto-d-series-hd-front-axlepdf/

Garry
 

Edited June 8, 2015 by gwest_ca

["D"- Man 827]

Thanks Garry,  That's probably what it is.