I know there's 2 difference kinds for DDO-001 . Here's a good article by Ken Potter http://koinpro.tripod.com/Articles/1969SDoubledDieCent.htm
It turned out to be Wexler DDO-002 http://www.doubleddie.com/311222.html Which is also Coneca DDO-003 and falls under stage A . http://varietyvista.com/02b LC RPMs Vol 2/1969SRPM003.htm