From research done years ago I seem to remember these being supplied by the Wine company. 1/2" round bar bent into a loop and the distal ends were bent out to about a 30 degree angle which separated the loop from the car sides allowing the tie-downs. Those distal ends were electric welded to the side. Most HO models of these are flat to the car side and don't project out at all. Years ago I took some 0.006" wire and bent some for this purpose, but I felt the effort was not worth the appearance. The CA glue did a reasonable fine job of emulating those welds!

My early work on making a resin 29' Greenville 1953 built WP coil steel gondola had these clips. These prototype parts were not welded to the bulb angle, but rather to the field of the sides.

-Andy Carlson

Ojai CA