1969 engine VIN discussion

Cast in 6/25/68 (or 8/25/68) and machined and built in 12/27/68. That's almost the middle of the production year. They started stamping blocks in mid year of 68 and all 69's had full vin stamp right? Or is that all hearsay?
Just think of how screwed up stampings would be if all of a sudden you had a stamp with 13 characters. Screwed up like this one is.