WAO Part 3: Numbering

With the coming of digital I needed a system that came me more that a simple roll number. In fact, digital all but eliminates rolls. I decided a some point to retain the metaphor of the "roll" but changed the name to "set". Today everytime I download a batch of pictures, I designate that as a set. Sometimes a set contains 12 images, sometimes 1200. I use the following number system now to get a handle on the image.

0501A.DM_0001

The first two digits "05" is the year. ie. 2005
The next two digits "01" is the annual serial number ie. "01" The first set of 2005
The fifth digit "A" is an extra number for future needs. A=Means that the roll number is correct. X=Means that I'm not sure if the roll number is correct. Given the inconsistent numbering of some of my original media, I must rely on a guess. The "X" means that I should check these images.
Period. (Divides the set number)
The seventh digit is an alpha chracter that indicated the medium of the original image. With scanning I need a way to know where the original image came from. I have a list of these designators. "D" means digital original. "T" means color slide.
The eight digit indicates the original capture device. "M" means Canon 300D. I have designator for each of the cameras I have used over the years.
The last 4 digits are arbitrary. The camera provides this number when I shoot digital. When I scan, the scanner serializes the images as they are scanned. When I'm scanning prints I add the number. I make no attempt to serialize this number to the actual slide or negative.