The DC-5 was a twin engined plane, almost a head on competitor to the Convair CV-240, I think.
It must be considered a failure since only about a dozen were sold to one customer, KLM.
It's main disadvantage was probably that the world was full of cheap ex. military DC-3s which did not do the same job, but almost, and at a considerably lower price.
It also hit the market at a time (the Korean War) when all US aircraft manufacturers were very busy building "a new Air Force", so Douglas had little encentive to promote it.
When the market was ready for such planes, then more capable planes like the Fokker F-27 were available.
Best regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs