Darling Freight Inc
Grand Rapids, MI
MC-046280 DoT 75813
Renamed Key Line Freight Co 1971
Route Map - Spring 1961
Profiled in Mike Terebecki's The Trucking Pioneers Book II (click image to see Book index)
Patches of it that are in my project - Facebook Trucking Industry Insignia Patches
Other known patches
If you want your own memoribilia:
Items available on eBay
Note that patches sold by "freedomfifty2k" and "bob82ndabn325inf"are likely promo/replica patches, not patches actually used by the company represented.