Hi,
It was only ion early 1916 that Units were required to issue documents at all. Many had by then already issued docs on their own initiative, but many early 1916 docs are "catch ups" for guys who had recieved awards but no docs in 1914-15.
I had floated this theory for a few years, based on observation, then the Wernitz book nailed it by finding an order/Statute.
By 1917 things seem to have been more or less up and running... I would say (as a rough rule of thumb) docs usually followed a few days to sometimes a month or so after the award.
It is only possible to know when you have one of the docs with an award date AND the date it was signed.... or if there is a Militärpass with it.