Yes, there is a difference... Also, take note of the plating on the light- the (gold?) cad and the other plating on the body. Doug, is the inner area (the backside of the inner housing) painted white? The 68 to the early/ mid 69's are painted white inside the housing. The mid-late 69's are silver, almost like a silver chrome..
George, this one is painted white you can see it if you zoom in on the one pic on the edge and I believe it to be a 68 as most of the 69's were all plated the same gold color although carried the same part number. I personally never seen one painted anything but white on the inside but I am sure there were variations.